What caused the decline of the RTS genre?

RTS is one of the genres with the highest skill floor out there, many mechanics that are core to be able to win the game are not really intuitive, games tend to draw long, so a bad player have way too many opportunities to throw a game, and because luck doesn't really play any factor (that isn't bad in itself, fighting games usually don't involve luck either, but they are often short, so a new player can eventually win a round over someone better due to a mistake/carelessness), so if you play against someone better than you, you lose 100 out of 100 times, and because of the high entry difficulty, it often takes a big amount of games+research to be able to have any chance. As it turns out, people don't like to lose (especially when they can't even understand why) so the influx of new players is inevitably low unless the game itself is deep rooted in the gaming culture (like in Korea, where StarCraft is still firm in its place). Also, at the time RTS was a popular genre, games were kind of new and a "nerd thing" (maybe justifiable, considering that RTS was popular lol) so both bringing new players into the game and teaching them how to play were difficult tasks. That said, I do think a ressurgence is unlikely, but not impossible. If a RTS manage to blow up in the future, many of the problems of the past would've been resolved/facilitated, so my major concern would be about marketing. Think like what Riot Games does to League of Legends, they spend shit tons of money to make those big shiny international events (and believe me, in isolation, they are a huge finantial loss) to cater more players, to make people say "wow look at this guys, they are soo good, and playing is their job, I want to play as well". If whoever makes/publishes/market about that hypothetical RTS banger doesn't or can't commit to doing something similar, the game will be doomed to become as niche as Smash Bros Melee (literally what happened to the game lol)

its EA games fault

Bruh try playing an RTS on your phone. I can barely play MLBB as is