Why is bad chat more punishing than gameplay troll?

The punishments are the same, but it's easier to detect and track verbal abuse than gameplay. That's all there is to it.

it's all punished? i don't understand the point of this post

It's really not. However it is a lot easier to prove. Trolling requires a live person to review games. And 1 game won't get you banned it requires a history or SEVERE assisting enemy team/feeding/harassing teammates.

Chat bans are a lot easier and quicker to review as they do not have to watch entire games but can read/automate chat logs.

They will get banned if they have a history of trolling it just takes longer.

It's harder to detect than toxic chat. Take for example w. He can eat allies to save them get them into position etc. However more than once I've been trolled by Tahm by him eating me and "saving me" when I was trying to dive the back line. Stuff like that would be hard to detect I would assume.

Things like spamming wards in the base and buying multiple tears they can detect, and has been part of why people were banned in the past.

Who says that it is?