>>724795742
A combination of other genres emerging that focus on one particular aspect of the RTS that the old audience liked (e.g. city builders and other management sims, RTT games like Wargame and Total War, and so on) and over a decade of RTS developers constantly chasing the Starcraft-tier competitive multiplayer/esports dragon without realising that only represents a minority of the remaining audience still interested in RTS games.
A lot of developers/publishers still haven't figured out that virtually all of the big competitive multiplayer smash-hits started with a good game that generally popular that people got invested in enough to take it super seriously, and that trying to skip the general audience step and building a game entirely around super sweaty comp multiplayer almost never works. It does look like that mentality has thankfully mostly disappeared now, but that's probably because most of the studios still making RTS games today are small A/AA outfits and serious big budget projects basically don't exist in that space any more.