Activision Blizzard tried to buy the rights to Dota 2 from Valve
On his Weibo page, famous Chinese caster Dong "DC" Can said that Activision Blizzard tried to buy the rights to Dota 2 from Valve. The commentator didn't give an exact date when this happened.
According to him, the deal fell apart because the companies couldn't agree on a price. Activision Blizzard offered too low a price and put their interests above all else. Managers of Valve took part in the negotiations, and Blizzard had no conversation with IceFrog.
Dota 1 was originally a mod for Warcraft III, an Activision Blizzard game. One of its creators, IceFrog, began working with Valve in 2009. A full-fledged game came out from this studio and was called Dota 2. Later, Activision Blizzard tried to sue Valve for using the Dota brand, but without success, because according to the Warcraft III user agreement, the modifications weren't the property of the studio.