Look, this is simple:
The Feds are accusing him of falsely claiming the election was stolen.
To prove it they need evidence that shows he knew it was not stolen.
If it WAS stolen, he can’t possibly have known it was NOT stolen.
Therefore, regardless of what Trump knew when, their entire case hinges on whether or not the election was in fact stolen.
Trump is very smart to publicly double down on his claims that the election was stolen - because ultimately, the Feds are going to have to prove the election was not stolen - and they can’t - because it WAS.
Assuming we know what the evidence is going to be, which neither of us know.
The Government doesn’t have to prove the election wasn’t stolen, what they are alleging is Trump was trying to overturn the results of the election and engaged in a conspiracy to do so.
Stolen or not, the result was Biden became POTUS, if and it’s a BIG IF, the government puts multiple Trump aides on the witness stand saying they all knew the election was lost before election day and before the results were announced that will be major damning evidence.
Assuming you are right about the burden of proof being on the government to prove the election wasn’t stolen, they will put on tons of evidence pointing out that despite allegation after allegation by Trump, not ONE allegation has been proven in a court of law and they would be right.
The burden of proof over the election being stolen is going to be squarely on Trump.