There are multiple private server implementations. Blizzard does not hunt them. They are on github, you can run it in your basement and play with bots and some friends. I don't know if that presents a copyright violation, but as a matter of fact, Blizzard doesn't care enough to even submit a DMCA to GitHub.

Funny fact that both Blizzard and GitHub nowadays owned by Microsoft, so in the end, Microsoft hosts private server code for its own game.

But if you're taking this code, host it on a powerful server for everyone to join, integrate shop to extract money from players, advertise it as a separate game. That's basically running a company which extracts money from Blizzard IP. That crossed the line.

I'm not the one to protect Blizzard, but in my opinion they're doing the right thing here. Turtle WoW attracts players who could be paying subscription to Blizzard and play WoW Classic.