I do not think that most players love horror games. I think this is one of those situations, where intuitive grasp of statistic fails us humans, yet again.
If you look at Steam, it is just one category among many. And I see no indication that horror is in any way more popular than other categories. To the contrary. You can't market true horror to kids.
They are obviously popular among devs and people clicking games for popular browse sorting on itch. That is what we observe, and wonder about the reasons. Judging from the many threads complaining about horror games, it might be, that horror is more popular among the devs, than it is with the players. If you look for it, just about any thread wanting to filter out games, is asking because they do not want to see so many horror games or visual novels in browse. Wich makes me think, that, no, not most players love horror games. But enough to skew browse results.