Yes, if you try to prosecute Trump, you all but guarantee a civil war.

Again, Brits just don;t understand America or American politics at all.

I will believe that Biden has actually won if and only when:
a) all of the legal challenges have been exhausted and Trump has no legal avenue remaining but the Supreme Court
b) the Supreme Court (SC) actually rules to affirm all and every ruling of the lower and appeals courts in every jurisdiction
c) Trump voluntarily concedes and acknowledges the result

However, the SC has been indefatigably groomed and stuffed with conservative originalist/textualist (simplistically: the Constitution must be only interpreted in the language of the time in which it was written, modern ideas or values can never play any part in legal interpretation thereof) acolytes by the dark-money funded Federalist Society (though the Mercer family of Cambridge Analytica fame were long time kingpins funnelling money to them).
Under the relentless hand of Leonard Leo for the last 40 years, this group of about 70K members is one of the real powers behind the throne. This unappointed small special interest group alone have now hand picked 6 of the 9 Supreme Court Justices (SCJ), and each of their picks was chosen for their ideological purity and adherence to Fed Soc doctrine.
It is for times just like this that that power has been consolidated. It is why Senate Leader McConnell illegally denied Obama the replacement SC pick for SCJ Scalia's seat in 2016, refusing even to give a hearing (as required by the Constitution) to nominee Merrick Garland for 9 months, allowing Trump to appoint Fed Soc darling SCJ Gorsuch.
It is why Justice Kennedy was pressured to retire in 2018, clearing the way for Trump to appoint the Fed Soc loyalist SCJ Kavanagh.
It is why McConnell acted in direct contradiction of all of his many 2016 arguments to the contrary, and rushed through the shortest ever confirmation and the closest ever to an election, allowing Trump to appoint Fed Soc acolyte SCJ Coney Barrett in the shortest time ever.

After Watergate, prominent Republicans met and decided that process was unfair, or undesirable. Yes, their guy was a crook, but it was inconvenient that they had no avenue to keep him in place regardless. So, they drew up wide ranging plans to deal with everything that they believed would be required, should a similar situation ever occur again. Almost no one took them seriously, the plan would take decades and require radical transformation of the entire landscape of America contrary to the direction of travel at that time.
But, they doggedly stuck at it. Little by little, piece by piece, they broke down the norms and accrued soft power at every level in every state that they could. They remove the fairness doctrine to allow cable news channels to have no duty to the truth, and fast-tracked Rupert Murdochs citizenship so that he could set up Fox News and other media assets to provide a permanent drumbeat to reconfirm Republican orthodoxy. They similarly fixed for donors and loyalists at Sinclair to obviate monopoly rules so that they could completely corner the massively influential local news market (most Americans, even to this day still get news mostly from local TV, mostly owned by Sinclair who obligate their stations to run Republican borderline propaganda or lose their franchise). They did the same for Talk Radio to allow special dispensation for Limbaugh, Levin and the multitudes of hugely important and influential talk-radio hosts.

And on and on, in every sphere of influence, they bent the shape of America to their will. Every position in every election down to dogcatcher (yes, really) was leveraged to accrue as much power to Republican hands as possible, and to remove it from Democrats if they won elections - such as recently in Wisconsin when the State voted in a new Democrat Governor, but just kept the balance of power of the State Senate in Republican hands. The outgoing Governor, Scott Walker in his last days before the investiture of his successor passed a bill that stripped almost all of the powers from the Governor and gave them all instead to the State Senate, where Republicans still held the balance of power. The State had voted for Democrats, but all of the power was transferred seamlessly to Republicans. There was nothing explicitly in the laws preventing this. The Founders of the state could not possibly have conceived of a group so venal as to have endorsed it.
As with so many things both in US, UK and everywhere else, the space where previously we would have presumed fairness or decency would simply have prevented such things under common understanding, were left to the honour system, gentleman's agreements, and implicit assumptions of fairness. Ripe semantic and legal territory for 'disruptors', lawyers and power-grasping would be oligarchs.

This sort of thing is so commonplace that it doesn't even get reported in America. I'd be surprised if any Brit reading this knows much about it though.

On and on, relentlessly, and still America, and especially the short-sighted impractical Democrats did nothing because they could not believe the sheer scale of the plan.

But now, all that power has been consolidated. All that power has been protected.

Because when you have spent 40 years laying the groundwork to get exactly the judicial rulings you require, eventually you have all your pieces in position and you get to play your move: you get to dictate exactly the judicial outcome you require.

If you want to, you get to overturn an election, all quite legally; in that space between the laws exactly as written and the assumptions of what a society would naturally and righteously consider unconscionable.


Now, McConnell and the rest of the real puppet masters may actually decide to let this one go. As explained before, the Presidency at this point means almost nothing to them, they have the balance of power for at least the next 50 years. It amy be more profitable to them to once again crash the economy just prior to, or under, a Democrat President and endlessly repeat, 'look, look how badly they ruin our country, don't you want the strength and stability of us back?'. Then, reap a landslide in 2024, rinse and repeat the playbook of the post-Watergate era.
Ultimately they'll get to a Constitutional Convention - their real end goal, which they've been quite open about since the mid-80's. I won't go into it completely but basically you get to rewrite the Constitution quite legally and however you want. The founders weren't stupid, they saw this sea change event as a dangerous affair if the country were to devolve into party based factionalism, and feared it. They railed against p\arty loyalty for good reason (read for example, George Washington's farewell address). Party loyalty means putting something before the country, and so they placed a very high burden of power to be required in a very high number of the states and Federal levels of government such that if it were ever to happen it would reasonably reflect the overwhelming will of the collective people of the country.
Modern Republican are very close to meeting those requirements already, so they probably don't need a Trump Presidency.
But they'll try to keep him around because he is so lucrative to them - he is amoral, not immoral. He doesn't care how corrupt you are so long as he gets a cut or some quid pro quo out of the deal. White collar crime - the sort that enriches politicians and those in the sphere of influence - is all but legal for Republicans under Trump. That is very useful, someone without conscience that doesn't balk at any largesse you may care to run.
Also, the Republican party is no longer the Republican party. I don't mean that they have forgotten their values, principle or ideals, though they have, all three. Trump's supporters are loyal to him not Republican Party operatives or management. If you anger them by treating Trump unfairly & and he, of course, believes EVERYTHING is ALWAYS unfair to him - then they will turn against you. Republicans can't risk fracturing their new base of support, and so have to be seen top be fighting for Trump, tooth and nail. Many also have been converted to Trumpism, the noise upfront provides perfect cover under which any number of otherwise sensational bombshell outrages have been quietly passed through to law.

So, yeah:
TLDR: Biden doesn' 'win' until SC says so, that will only be if Republicans have decided that losing the Presidency is of more value to them than keeping it.
Even then, Biden loses. Democrats have no meaningful power or route to such power for decades at best.