Part of it is because there are still looming constitutional questions about whether a president, current or former, can be indicted for his actions during his presidency. I think we've mostly resolved those, though. A substantial and powerful cadre of political thugs is still going to try to sue to throw every conceivable barrier in the way of a reasonable interpretation of the law, but that just takes time to wade through the bullshit.

Another big problem is that Trump captured a huge amount of the judiciary, at all federal levels, by putting cronies into high ranking judicial seats. It's the main thing Republicans have been doing for, like, 50 years. Putting a case in front of any one of those is a landmine, and that minefield has to be carefully navigated, and that also takes time. We're basically done with that part, now.

The much bigger problem, in my perspective, is that any criminal trial requires a jury.

Almost 50% of the voting public voted for this motherfucker. His approval has dipped sharply since then, but still, a huge portion of the US public is willing to do just about anything to make sure "their guy" wins. They have proven nearly invulnerable to rational argument, emotional argument and any appeal to empathy or compassion. They will lie to get on that jury, and then they will vote for his acquittal if they don't get caught. Voir dire--the process of choosing that jury--is going to be one of the most harrowing things any prosecutor ever has to do. And it has to be done correctly because it's extremely important that once the wheels of justice start turning, that they reach the correct verdict.

Any thinking person knows what that verdict has to be. But there's no guarantee that we'll get it.

And if we don't get it, we see the rule of law start to collapse at all levels. Remember the 1992 riots after the cops that beat Rodney King got acquitted? Imagine a whole country of that. The prosecutors in these cases are thinking about that. And that's why they're being extremely meticulous about every detail of these proceedings, because their errors could cost us a lot more than Trump getting away.