I'm curious why they ended up focusing on DOTA. Prize money? Valve make the game particular amenable to machine interface?
* limited choices for actual commands to make, but still lots decision to make.
* a very active competitive community
* easy to evaluate win conditions and (I think?) somewhat easy to evaluate “am I doing well” conditions (like if you fall behind on experience you are doing poorly I think)
So maybe it is a convenient genre.