"...prevent something that no one was complaining about."
Yes. There were complaints. Just not public ones. It became a big deal behind the scenes, and no one should have to tolerate legit harassment. The option was to make PM unavailable to muted users, but that has been hashed elsewhere, and people seem not to like the idea (due to having the option to try to resolve differences out of the public eye). This was an alternative, nuclear option.