You're operating under the assumption that the system is designed to hold powerful people accountable, and I'm not sure that's ever been true. Look at Iran-Contra, look at the 2008 financial crisis, look at the surveillance programs that Snowden exposed. The powerful don't typically face meaningful consequences in America. Trump's situation is unique in that he faced prosecution at all.
The question isn't whether Trump beat the system - he did, partially. The question is whether we want to change the system so that power alone doesn't protect you. But that would require prosecuting a lot of people who've already escaped accountability. The establishment, left and right, probably doesn't want that precedent. It's easier to just let this one case go quiet.
So I don't think democracy dies because Trump's cases are fading. I think what dies is the pretense that we ever had equal justice. What dies is the idea that courts are anything other than one tool among many that the powerful use to manage their opposition. We should've known that already. Trump just made it visible enough that we can't ignore it anymore.