Are the cases falling apart? If by that you mean the evidence that will be presented if they go to trial, it seems that answer is "no". There is a lot for Trump to overcome there.
If however you mean will the cases be delayed past the election and assuming Trump wins all be left unprosecuted, then for the federal charges there is a good chance they will fall apart. That is why the current NY case and the GA case are most concerning for Trump. One will complete, and unless the defense already did a good job of finding one juror who will hold out for a mistrial, that case will likely end in conviction. Still, the sentence will likely not include jail time, so campaign goes on. The GA case could still happen even if he gets elected, though likely delayed until 2029, which gives lots of time both for a new DA to take it over or for GA state politicians to find a way to kill it.