Off topic, professional gamers aren't really that professional. Maybe that one specific genre of games that they dedicate their lives to playing, but sit them in front of any other genre of games and they'll be worse than most good gamers. All those dude bros who play only Call of Duty are pretty much casual gamers, the same could be said about Daigo Umehara who plays fighting games almost exclusively.
E sports is profitable for the companies who get in on it and the gamers that want to waste away playing the same game. It's become really popular because gamers in general have become garbage at playing even the most simple games, they'd rather watch other people than play because they don't want to take the time to get better, the very reason we get yearly franchises that hand hold your way through the end, the reason why walking simulators and visual novels are starting to become such a big market, because most of the gaming fanbase nowdays is complete garbage. They're also very stupid. Paying let's players through Twitch and Patreon to watch them play games, and we all know about paying out the ass for worthless DLC, the very reason why it's became so bad and gets worse year after year.
*edit*
Gaming has become more of a money grab for a lot of people than the passion for the entertainment itself.