You say that, but there's actually quite a few up there for all time peak that have been from the past few years. Realistically, it's that single player games just don't have the replay value to get most people to spend hundreds of hours in them. And that makes sense. But the all time peak player counts
#2 black myth wukong at 2.4 million Game journos hated it, but gamers who like souls games actually liked it
#9 Elden ring at 950k same reason as above
#12 Hogwarts Legacy, 879k and game journos spent more time hating this one that black myth wukong
#13 BG3, 875k
#22 fallout 4, 472k but this is a decade old and is basically irrelevant(shit game anyway)
#25 monster hunter wilds beta, 463k. it's honestly kind of pathetic that shit can't do this well
Now if you sort by 24h peak then yeah single player stuff is far lower unless it's been hyped to shit by streamers(like schedule 1). But is that really much of a surprise considering how few decent single player games actually get released? It's almost like there's a pattern of shitty games doing shitty for sales and player counts, and games that actually do what customers want readily making it into the top couple hundred most popular steam games of all time for usually just a single playthrough.