You have to weigh your current abilities and their earning potential vs. the costs of venturing into a new field.
Being at the top of Dota is easier than being at the top of Math or Chess or Go, since Dota is a newer field. They aren't really comparable, but you still compare them if you are trying to figure out what you want to put your time into.
Some people just get lucky and find the thing they are good at on the first try. Then they can maximize their hours available for that thing.
Other people (probably the majority) have to try different fields and start later, and ultimately have less time overall to spend.
So it actually seems rational (if maximizing hours-spent is your goal) to go all-in on the first thing that grabs your interest, which could be Dota.