There is a key difference here in that as you say the authorities are doing something. If we had random vigilantes going around mugging muggers that would indeed be a sign that we had a problem.

Not quite that, but rather vigilantes mugging you when you're most vulnerable, and then returning the money later when they're confident you can safely hold onto it.

I wonder if the vigilantes will return the money with interest...

"With interest" at least to me is a very greedy proposition. Those people just kept you from having zero ethereum. If anything, I'd personally give them reward money.

> the solution to that problem is an authority mugging those people

The authority and the process by which they do this is agreed upon, or at least known, ex ante. That was not the case here. Trust isn't fungible.

Mugging scales poorly.

That is so accurate