Steam has set a new multi-million user milestone, ending its first quarter with 40 million+ concurrent users.

PC gaming is on the rise and Valve's digital storefront continues breaking new records. Earlier today around 8:30AM EST, Steam broke 40 million concurrent users for the first time in history. The exact count is 40.26 million by Valve's official Steam Charts, and 40.27 million by SteamDB.
It's worth noting that the vast majority of these users weren't actually playing games. Out of the estimated 40.27 million accounts that were logged into and using Steam at once, only 12.8 million of them, or about 31%, were playing a video game at the time. It's hard to say what the others were doing but they could be buying games and/or content. Nonetheless, these are incredible numbers and Valve also set a new all-time concurrent in-game player peak as well.

Steam remains the premiere storefront for PC gaming, and early reports from the FTC v Microsoft court case of 2023 show that Valve made $7 billion in revenue throughout calendar year 2021. Gaming has grown and changed in a number of ways since then, with the PC segment alone seeing substantial uptick over the last four years.
Bloomberg estimates that Valve's Gabe Newell is worth around $6.89 billion.

According to Newzoo, PC gaming has grown from a $35.9 billion contributor in 2021 to a $41.5 billion contributor by 2024, with a Compound Annual Growth Rate (CAGR) of ~3.7%.
It's unclear what Valve's current revenue is currently like, but consistent best-sellers like Black Myth: Wukong, Palworld, Helldivers II, Counter-Strike II, and more recently Marvel Rivals, and even Monster Hunter Wilds--all of these games have helped surge per-unit game sales revenues on Steam.