Conceptually, LoL filled a hole. DotA was DotA, complicated, hard, lots of nuance. Some people wanted an even more complicated DotA. Heroes of Newerth filled that hole. Some people wanted a simpler DotA. LoL filled that hole.
I personally preferred HoN, but I can't fault people for preferring LoL.
This is incredible
Right next to each other lol