You registered almost two years ago but never posted, so my only guess is the account name you had registered and sitting there is similar to someone popular (who apparently has access to some server these people asking you also want access to), and people have been confusing you for that person?
It's either mistaken identity (unlikely) or a gaslighting misdirection scam. I suggest you ignore it.
Perhaps someone has stolen your current username or by coincidence has the same one.
Also isn't Deadmouse some famous rapper or DJ or the like? If a server owner is piggybacking on a famous name, they are likely to get trouble for it. Which all the more leads me to think this is fake and these messages are from a scam/spam group.
Famous names sound familiar and people often believe they are real (at least as a fan nickname, not the famous person themselves) as a result of the familiarity.
But in practice this usually ends up being a psychological trick.
If you want to discuss this further, I can add you on discord, but I think I've said everything useful.
Why would it be shared? Everyone is entitled to have a private server for themselves and their friends, even well-known artists. What possible motivation would someone have to suddenly open up a private server to a larger community? Do you allow just any old stranger to traipse through your living room unannounced? Of course no! So why would you expect that someone would allow others to do the same in the digital space?
Leave deadmau5 alone. He's cool. And if he has a server, and wants to keep it private, he's entitled to that. Period.
Think of others before yourself and you'll have a more fulfilling life.