Actually, it is VERY important for a player to have lots of fans, because larger fan base = more $$$ from endorsement deals.
There's a reason why neither Adidas nor Nike want anything to do with him.
There's a reason why Federer and Nadal make several times more money from endorsements than he does.
Djokovic has been the most disliked top player in a long time.
And yes, he did this to himself. Not only with all the stuff from the beginning of his career, but also with his shirt-ripping, chest-thumping antics, his arrogant smirks, etc. That kind of stuff may work in the WWE, but will likely rub most tennis fans the wrong way. Not only in the US, but around the world.
Add to that comments made in the past by his parents, and then there you have it.