I don't follow moba so idk
Because Dota is dumb and they think that raising the skill floor makes the game better but what it does is only make newbies and beginners not want to play the game. It also doesn't help that the devs don't care about the game and barely update it so players that have been playing the game are slowly getting sick of it and are starting to move away from the game. No new players coming in + inability to maintain the existing player base = steady decline