Oh I was listening to Alan Cross talk about this earlier in the week.
Basically material conditions for Zoomers (and likely everyone who comes after) are rapidly deteriorating and when that happens, music tends to get darker. Consider the Oil Crisis of the 70's, which gave us punk rock. When it all settled down around 77, we got disco. The recession of the early 90s, along with the Gulf War, spurred the rise of grunge. But when we believed that was over (say around '96?) the focus turns away from angry young white men with guitars and toward feel-good pop like the Spice Girls.
Spotify did a lot to disrupt these kinds of cycles, but they're not immune to them. During the mid 2010's, when we should have seen a return to big, loud, guitar-based music, we got a rise in folky indie stuff. But it was folky indie stuff that addressed those feelings. We want music that addresses our emotions but the ways we go about addressing our emotions require less volume these days. I suspect this has something to do with either men getting better at expressing themselves or fewer young people identifying as male?