Even DotA itself was inspired by Aeon of Strife which was a StarCraft map. There were a few AOS-like maps at the time but DotA became the most popular. Then Riot came along and approached an ex DotA designer to help them make a successor. They also approached the owner of dota-allstars.com which at the time was the main site for DotA. Discussions, hero suggestions, fan art, pretty much anything dota related was there. Then, the owner, Fuck Pendragon, took the entire site down and replaced it with a LoL ad. Ofc all those hero suggestions were taken and implemented into LoL without crediting the creators. A few years later he also tried to use blizzard to sue valve for the dota rights but blizz and valve settled it out of court without him.