I think the root of that is the high reliance on teammates and the level of commitment each game takes. Unlike League there is no early surrender, so if you’re in a rough game you have to endure the full duration which can last around an hour. If you feel like it’s your teammate, who is probably randomly paired with you, that is failing it’s easy to get frustrated. This is one of the many things that make Dota either extremely frustrating or extremely satisfying.