The first dota esports tournaments started in 2004, full history here: https://dota2.fandom.com/wiki/History_of_Competitive_DotA_(T.... The tournaments have been running for 19 years.
Even if you argue that Dota 2 was the true birth of these tournaments, The International 11 (the 11th yearly dota 2 championships) was held this October: https://en.wikipedia.org/wiki/The_International_2022
The first International was held in 2011, over 11 years ago. Invites to participate went out to the existing highly ranked dota esports teams - DotA was already established as an esports game at this time, which is why they were able to source teams from around the world to play.
In regards to your claim of lineage, in the same way that chess does not change between a wooden board and when you upgrade to one carved in marble, I'm curious as to why you see these as two separate games? Dota 2 was purely an engine upgrade rewrite of the original mod, without any gameplay mechanics changes. Dota 2 and Dota 1 maintained parity with each other until Dota 1 was deprecated in December of 2016: https://dota2.fandom.com/wiki/Version_7.00
They're the same game.