Not only have we not proven much in court and investigations, but many in the public see some anti-dem theory flop, and they assume all the dem cheating theories are wrong.
It's smart to admit the limitations of what has been actually "proven" so far, beyond what the Trump fanatics believe. That is the only way to escape the "of course it was stolen" mentality of so many. We can, and should, hope that Trump finally has the goods, and will deliver them. A lot is riding on this, and he will have had 3 years to gather his evidence by the time the trial starts.
That said, his attempts to delay the trial, and attack everyone associated with it, does not exude confidence.