Look, I get why this pattern seems suspicious and I've gone down this rabbit hole myself more than once. But you have to be careful here because "powerful person" and "witness" are such broad categories that confirmation bias does a lot of heavy lifting. We remember the cases that fit the pattern and forget the dozens that don't.
That said there are a handful of cases where the timing is genuinely uncomfortable and the official explanations have real holes in them. Epstein is the obvious one and I think most people across the political spectrum can agree the circumstances were at minimum embarrassing for everyone involved in that custody arrangement.
The thing that actually bothers me more than any individual case is how quickly these get labelled conspiracy theory and shut down before proper scrutiny happens. Healthy scepticism of institutions isn't the same as thinking lizard people run the world. Would be interested to hear if anyone has specific cases they've actually researched properly rather than just seen a tweet about.