Maybe the ECB knows or plans something on a large scale we don't yet know about. Corporations and institutions don't fight clean. We already know what their opinion of Bitcoin is and that they will do everything in their power to have it destroyed. One way to do that is attacking the security infrastructure that preserves the network. They are not going to do it like that because they would look like the bad guys. But if you wrap your plans up in a colorful package explaining how a bitcoin mining ban stops climate change, makes life on earth more sustainable, cleaner, and safer for everyone, you will get enough idiots on your side. Getting their corrupt friends to accept their plans of a EU-wide mining ban coupled with the same thing in the US would create devastating consequences.
Self preservation. As soon as they lose the ability to control your money, they lose all the power and relevance they ever had.
I would love to live in that world one day. I just don't see that happening in my lifetime. A worldwide revolution is required against centralized institutions of power. But this terrified population isn't going to do anything. A small minority will and does from time to time, but they get dealt with quickly.