You're not just looking for conversation.

Unless you get a response from the site admins, anyone's answer is pure speculation. No one is going to be able to say, definitively, why .ml was chosen, except the site admins.

My theory is: .ml domains used to be offered for free. So they made lemmy.ml for free, as it was just a toy project. Then, they upgraded to the paid .ml domain (which is how they managed to avoid the recent free .ml purge).

The "its Marxism-Leninism" could be true, but unless you get an answer from a site admin, everyone asserting that it's true is talking out of their ass. They don't know any more than you or I know.