The EU decided that it rather doesn't have any platforms than some which allow hate/propaganda/childabuse. The intent is to fight the mentioned things and ideally remove them from society. By and large, this decision is a democratic one and fine.

Platforms may continue operation, if they promise to remove all stuff. Here there are two options, one stipulating that all content needs to be checked before its published. Thats the draconian approach. Currently its fine to only go after user reported stuff.

Now to your first question: They fon't gaf about musk and don't care if he removes the stuff. But if he choses not to, they will shutdown twitter for europeans. Thats why they adress him, because he as a major shareholder and CEO (is he?) calls the shots there.