He was functionally immune from prosecution when he wasn't president. If they want to actually try to rein him in now they're gonna run up against the supreme court ruling that says that anything he does as part of being the president he's already immune from and a potential (one would say extremely likely) future supreme court ruling that hinges on the idea that the constitution never explicitly said he can't pardon himself. I guess this is better than just rolling over and doing nothing but I'm pretty jaded on the idea that the law will ever tell the wealthy what to do in a way that actually compels them to listen.