CK2 did have the Shattered World setting, which can setup a game where each county starts out as an independent ruler. I assume actually trying to play it as a multiplayer game with a decent quantity of players would run into netcode issues though, Paradox games seem to struggle pretty bad with crashes and desyncs when the player count goes up (and besides, even if they didn't, you're probably going to struggle to find several dozen other map sickos to play with you for hours each day )