Gaming is just a much bigger market than a lot of people seem to realize, niches can still be profitable and so you'll just see more and more of those types of games, making it seem like a trend, even if you look at it from an overall market revenue standpoint they're still pretty niche. Like you might think there's a trend for more and more unoriginal sports games, you wonder if they'll ever stop making so many, but even so those only account for ~12% of the market. (https://www.statista.com/statistics/189592/breakdown-of-us-v... and broken down slightly http://www.mweb.co.za/games/view/tabid/4210/Article/28870/ES...)
Plus anything that is cheap to produce that still makes a profit will tend to have more representatives. I doubt I'll ever play any of those anime visual novel 'games' Steam keeps showing to me but sometimes it feels like that's a trend that won't go away, and I have to wonder if I knew an artist whether he and I could make one that would sell if not well, at least generate a bit of extra income even after the cost of the effort. Meanwhile it'd be fun to work on something like Dark Souls but that's not the sort of game you'd want to take on solo or with a tiny team. Similarly there are lots of indie "8-bit" or just "pixel graphics" games I'll never play, but I find that I usually object to them more on gameplay rather than their often lazy art. e.g. sometimes I find something fun like Rabi-Ribi... Meanwhile Cuphead looks like a good game that also has a way different, you might say truly retro, art style but I don't really have an interest in playing it since I've never had a desire for more of that art style plus I feel like I'll just be disappointed it's not Contra 3 in terms of gameplay.
Additionally something being unprofitable doesn't mean people won't still make loads of it :)
My unscientific anecdotal experience with the European game dev scene suggests that the vast majority of indie/small developers are people working on their first game who then go out of business upon release and/or are funded by government funds for "creative media" and the like.
Plus anything that is cheap to produce that still makes a profit will tend to have more representatives. I doubt I'll ever play any of those anime visual novel 'games' Steam keeps showing to me but sometimes it feels like that's a trend that won't go away, and I have to wonder if I knew an artist whether he and I could make one that would sell if not well, at least generate a bit of extra income even after the cost of the effort. Meanwhile it'd be fun to work on something like Dark Souls but that's not the sort of game you'd want to take on solo or with a tiny team. Similarly there are lots of indie "8-bit" or just "pixel graphics" games I'll never play, but I find that I usually object to them more on gameplay rather than their often lazy art. e.g. sometimes I find something fun like Rabi-Ribi... Meanwhile Cuphead looks like a good game that also has a way different, you might say truly retro, art style but I don't really have an interest in playing it since I've never had a desire for more of that art style plus I feel like I'll just be disappointed it's not Contra 3 in terms of gameplay.