Sorry if this is cringe but I mean we have several "trendy" games that are horror (Fnaf, Hello Neighbor, etc) and two non-horror "trendy" games, that being Undertale and Cuphead. I feel the two non-horror games are more unique because they are not the same genre as everyone else *horror* and their gimmicks are more defined (Undertale with its morality and Cuphead with it 1930's cartoon art style, which reminds me of Tom and Jerry) It would give out some more variety (and maybe make me play them more often) but there is little space for variety in trendy, isn't there? (Shucks...)
The reason why Horror games are more Trendy than non horror games is bigger more popular gaming channels (Youtube and Twitch) play them. I remember when Call of duty modern warfare was the biggest thing in school. It's all about being shown to the world by massive content creators as advertisements are becoming pointless and more difficult to get to people.