That statement is a bit misleading. The damage an attacker can do through a 51% attack is much more limited than that. It allows an attacker to censor transactions or perform double spends, but it does not allow them to "redefine Bitcoin" (e.g. change consensus rules, arbitrarily reassign coins, etc.).

Why can’t such a bloc for example rename Bitcoin to Buttcoin?

Anyone can do that, it doesn't require 51% of the hash power. And it's already been done hundreds, if not thousands, of times (the more technical term for them is "shitcoin").

51% hashing power doesn’t prevent forks. Including forks to 51% of the token systems.

That’s the thing people thing of crypto coins as math, but they’re still a social construct.