This is the game and apparently it arrived on steam via early access on march 24, 2016 and just came out of early access yesterday which is the 13th of February, 2020. Just like the title says it seems to be Diablo like and apparently its having some sort of server issues that is preventing online Co-op play between players.
As of right now..
Also considering today is Friday(where I live at least), it might go above even more tomorrow regardless where it reaches its peak count tonight.
Edit: As of Sunday, it has now reached 124K players and also the servers are back up!