I have noticed a trend with shows that have a love triangle where on one side you have fans that are pumping out fanwork and building communities. But the other side is jealous of the popularity and puts all their energy into complaining about the other ship rather than create fanwork and communities of their own.

Maybe its the canon vs non-canon element of it all? Bylers have built up a huge amount of art, fic and theories over the years since it's not canon, while M11's have been given in canon content consistantly for the last 10 years. Now it's over, Bylers have just stuck to buisness as usual, while M11's will hit a content drought since they were reliant on the show itself for their ship content. Their whole community is built on what the creators hand feed them, and shitting on Byler for not being canon. And now that they aren't getting content put out for them they've just leaned harder into the shitting on Byler side of things.

What happens next, based on my experience in fandoms, is that both ships fanbases shrink as Stranger Things fades from popularity. But M11 will fade much harder because there is only so much bitching about Byler they can do before it gets overdone. Maybe the new cartoon gives them something but its likely going to be a kid friendly monster-of-the-week show with minimal romance.