Not doing something like this leads to stupid stuff like having POTUS' handle be "real donald trump" (yes, I know choosing that handle predates his being POTUS, but you get the idea).
I actually find this a charming reminder of the old days of the web. there's a certain populist quality to the idea that no one is important enough to snatch a particular username that some commoner took first. I agree situations like @realdonaldtrump are kind of silly, but it doesn't hurt anyone. anyone who actually has a large audience has a verified account so there's little doubt regarding who actually controls it.
that said, we really do need a responsible way to reclaim truly inactive accounts without enabling "reset my password via email" type attacks.
So yes, I think they should have at least asked first and tried to resolve it amicably.
No one should be able to get something any more than any one else. Of course that’ll never be the case. But why excuse the behavior and even encourage it?