League of legends especially..., was released in 2009 the same year bitcoin was released in both are different but have progressed a lot finance-wise.
Do you think Esports betting has a good scope in the future where most of the teens are getting into games like LoL and world of warcraft, Dota, etc?
Even if they don't hear this in ads they will most likely hear it from their in-game teammates.
It's already a huge market.
I don't think that there is too much uncertainty that the esports market is going to simply continue to expand its dominance. Especially after this pandemic period, esports growth has far outpaced any traditional sport growth due to restrictions.
As others have said, I think that bookies would be pretty dumb to not take advantage of this trend, and offer markets in LoL, Dota, CSGO etc. if they aren't already.