It’s much easier to prove something in the televised congressional hearings and the media because much of the evidence presented there would not be admissible in a criminal court.
The heightened standards in criminal court are because more is at stake. In a criminal trial, a defendant stands to lose constitutional rights such as liberty, property, and (in capital cases) life. So evidence has to meet certain standards, and not all evidence is admissible.
In a congressional hearing, the only harm a person faces is the truth coming out. Keeping the truth from the public is not a constitutionally protected right (even though Trump and the Congressional Republicans often act as if it is.)
Anonymous Sources
Much of the “evidence” you see on the news or read in newspapers would not be admissible in a criminal court.
One reason is because of anonymous sources. Major media can report “facts” after talking to anonymous sources. If the reporter is good and knows how to evaluate sources, the information is true and accurate.
But it can’t come into a criminal court as evidence because anonymous sources are hearsay.
Hearsay
At the hearing, Liz Cheney said,
You will hear testimony that the President didn’t really want to put anything out calling off the riot or asking his supporters to leave. You will hear that President Trump was yelling, and was really angry at advisors who told him he needed to be doing something more. And, aware of the rioters’ chants to “hang Mike Pence,” the President responded with this sentiment: ‘maybe our supporters have the right idea,” and Mike Pence “deserves it.”
Liz Cheney telling us what witnesses will say is double hearsay. In a criminal trial, the witnesses who heard Trump make such utterances must offer testimony under oath and withstand cross-examination. The defense will then try its best to discredit the witness, perhaps by showing that the witness has a history of lying, or a history of acting in his or her own best interests at the expense of the truth, or that the witness has an ulterior motive.
One problem with getting to Trump’s state of mind is that the evidence has to come from people in his inner circle, and many of them have a history of lying (or at least tolerating lies) because (to state the obvious) they are members of Trump’s inner circle.
I’ve compared bringing down Trump to bringing down a mafia don or a gangster. If the people around Trump are willing to shield him, it gets difficult to get to him. This is explained in The Godfather, in this passage:
[The Godfather] had given those orders in private to Tom Hagan. Later in the day, Hagen had, also in private without witnesses, instructed Clemenza. In turn, Clemneza had told Paulie Gatto to execute the commission. Paulie Gatto would now muster the necessary manpower and execute the orders. Paulie Gato and his men would not know why this particular task was being carried out or who had ordered it originally. Each link of the chain would have to turn traitor for the Don to be involved and although it had never yet happened, there was always the possibility. The cure for that possibility was also known. Only one link in the chain had to disappear. (P. 44)
To pin the crime on the Don, the Consigliere would have to turn traitor. If the Consigliere does turn traitor, the defense then goes to work trying to discredit him (which may not be hard because, c’mon, the guy is a gangster).
Because of the standard of proof — beyond a reasonable doubt—all the defense has to do is raise a doubt in the minds of the jurors.
A thing can be true and provable in court without rising to the level of “proof beyond a reasonable doubt.”
This is why OJ Simpson could be acquitted in a criminal court, where the standards of proof are high, but held legally responsible for the murders in a civil court, where the standards of proof are lower.