Amazon’s MMORPG called New World is the most successful PC game in the last six months. In the first 24 hours since its release, it has already been played by more than a million players, and yesterday it was played by almost a million players at the same time. The specific number is 913,634 users, making New World the fifth most concurrent player in Steam history.
It’s the best result of a single PC game from 2021 (400,000 players higher than Valheim’s record), and one day the New World could likely surpass Cyberpunk 2077 in fourth place games with a record number of active players. Out of reach are not even the permanent giants - Dota 2 and CS: GO. New World would need another 400,000 active players to break their record - if the servers serve it, it's not impossible.
The ultimate record holder in the number of active players on Steam is still PUBG: Battlegrounds with an incredible 3 million and 257 thousand simultaneous players. That record was set in 2018.
New World is in any case the most successful MMORPG on Steam by this metric, but that doesn't say much because many MMO titles haven't started their lives on Steam, and some like World of Warcraft aren't part of that platform anyway.