I think the inflation of an eSports bubble that is definitely primed to pop comes from the introduction of games that are FORCING some sort of eSports scene instead of letting it develop naturally. If anything, the bubble may have already been popped and it is slowly deflating because no one has realized it and keep trying to pump into it.
DotA and LoL are pretty successful because tournaments existed were ran and prized before developer support. They just put money into it to make it more accessible and lead to the high viewership of these events. The same applies to fighting game communities like Melee where almost all competitive events are player organized.
However, HotS and OW stumbled a lot because so much was pumped into it up front. But HotS is now a dead game and the OW team was scrapped completely earlier this year. So many of these players, as far as I know, have scattered to more established games to scratch their competitive itch.
Most recently in the MtG Pro League debacle which branded itself as the next eSport. Even though the game will continue strong due to years of enfranchised players, this is a obvious example of a company putting little effort into the eSports support only because they thing the turnover will be enough.
I do not think eSports - as a spectator sport - can evolve naturally. Mainly because, in comparison to physical sports - e.g. basketball, football, tennis, they are not easily accessible to spectators. Parents can easily watch their kids compete in the local TKD tourney, when they start turning up to watch them play in the local Rocket League then we can talk.