It was however only after DotA was handed[0] to the design/balancing BDFL IceFrog where it became the competitive game that we think of today. Before that, it was really just another yet popular "fun-map". He took advice from the best players and a trusted circle, but was known to have the last word on things.
There is something to say about the quality of a competitive game that is balanced around hardcore play versus a game that is balanced around a profit motive.
[0] I don't remember how the transition came to be.
5.54b was the last version before Icefrog, and then Icefrog took over development and the game slowly became the clean and interesting e-sport it is today. Was still just hobbyists doing it for fun though. People still don't know who Icefrog is, even after being hired by Valve he remains anonymous.
There is something to say about the quality of a competitive game that is balanced around hardcore play versus a game that is balanced around a profit motive.
[0] I don't remember how the transition came to be.