It was Chaos War (SC) -> Hero Arena (WC3) -> Attack on the Light v0.1a (WC3) -> Defense of the Ancients v1.3 (WC3).
Source: I made Chaos War (SC1 Map).
A multi-billion dollar industry hinges on the fact that an eight year old figured out how to make a map trigger which spawned units with an attack-move command in a custom editor in an RTS.
P.S:
(I've seen exactly $0 of DOTA "money". It was free and clear, for any and all, a source of happiness with no entry fee except Use Map Settings.)
Yes, it's consistent with what the genre was called before it was shortened to MOBA. "Aeon of Strife Styled Fortress Assault Game Going On Two Sides". A.k.a. ASSremovedS
I would say that was a strong influence but there were a lot of custom games with some of the elements of DOTA before it. I think DOTA defined the entire genre and how all the elements work first. Brood War just didn't even have the options to make a real MOBA.