Why not enough people played TT

It's because you just flat out ignored the entire game mode.

"Outside of the player population, Twisted Treeline’s art, map design, and even game pacing don’t meet today’s current quality bar and player needs."

All things that could have been fixed if you took the slightest bit of effort into improving it.

"However, Treeline has always suffered from low queue sizes, even in times when we added new items, map-specific champion balance, and even the Twisted Treeline redesign waaayy back in 2012."

I'm pretty sure it hasn't seen ANY form of an update since 2012 anyway? Seriously no one is going to play a mode if you just put it in the game and then don't touch it for 7 years.