Topics: Mechanics - Dota 2 Wiki
Valve's interest in the Defense of the Ancients property began when several veteran employees, including Team Fortress 2 designer Robin Walker and producer Erik Johnson, became fans of the mod and wanted to build a modern sequel.  The company corresponded with IceFrog by email about his long-term plans for the project,  and he was subsequently hired to direct a sequel.  IceFrog first announced his new position through his blog in October 2009,  and Dota 2 was publicly announced by Game Informer in October 2010. 
In total, professional Dota 2 tournaments had earned teams and players over $100 million in prize money by June 2017, with over half of that being awarded at the International tournaments, making it the highest earning eSport game by a margin of nearly $60 million.