Money and power. He has (or claims to have) alot of money and alot of people on the Right still seem to follow him, but I think that's more just based on momentum, there's really nobody else on the Right that they have that's as "charismatic" as Trump. The closest they have is DeSantis, and he's just some wannabe fanboy with no personality. I personally think Trump is pretty much done and washed up, the GOP just doesn't know what else to do at this point (certainly he still has a shot at the presidency, but I doubt it'll work out). The Right had one really good shot at a violent coup on January 6, and the only reason they really managed to pull anything off was because Trump himself was in charge at the time and he was able to subdue the Federal response to it.

I think one of the main reasons he's being treated with kid gloves is out too much caution of it appearing political. I think the DOJ is afraid of appearing partisan if the Democrat's #1 political opponent were to be locked up (regardless of how slam dunk the evidence is). In any other country, we'd assume that it was a dictator trying to tighten their control of the political system by locking up their opponents, and that's exactly what Biden/DOJ/Democrats are being accused of. Personally I think there's going to be some amount of protest or violence if/when he gets locked up/sentenced/found guilty/whatever, they may as well just do it now to get it out of the way. The longer we wait and the closer we get to the election, the worse it's going to get. It honestly won't matter how much evidence is trotted out during the multiple trials, or how many judges/juries find him guilty, Republicans are still going to bitch and whine about it. He's obviously guilty though, there's more than enough evidence.