To add to what the others have already said: One interesting thing about Dota is that it is a slower-paced game which isn't heavily reliant on twitch reflexes.

To add to what the others have already said: One interesting thing about Dota is that it is a slower-paced game which isn't heavily reliant on twitch reflexes. To win the bot needed to show good teamwork. Dota2 also has a developer-friendly "bot API" and replay system. I'm certain these affected their choice of game as well :)