Because two wrongs dont make a right. He was toxic and had been known for breaking the rules constantly. If you watched his video you could see he was almost always Chat Restricted. Because of this it was pretty obvious he wasnt going to reform, plus it was only a 2 week ban. You also assume they dont punish people who troll despite not understanding one is easier to handle than the other. Finding a toxic person is easy. All you need to do is look in the chat and chats from previous games. Whereas a troll might not look like a troll and could just be someone who had a bad game, or is new to the game. To flat out ban someone for not being good would lead to basically every single person at one point in their league career to have been ban which is wrong.
Plus you are defending him. You are basically saying because he was good (and to an extent a content creator you enjoy watching) he should have gotten away with it, basically implying he should be treated differently than everyone else. Riot does run like that, and if anything puts people like him at a higher standard because of their influence on the community and its obviously something Riot and the community does not want. We dont want Trolls, Feeders, AFK, or Toxic. But sadly we dont live in a perfect world where we can easily identify when someone is going to act out, or break the rules. Nor should it be acceptable to break the rules just because someone did something worse, or started it first. This doesnt work in the real world and it isnt going to work here!