Confused about ban

so just got banned for getting report in 1 game. In the game I got mad at a teammate who very questionably left me to die in a fight we could have won. I typed in chat asking if he was trolling,(because it littearlly looked like he was trolling), and he replied by saying "it's preseason ranked no one cares about winning". Despite being angry, I didn't speak much in chat after that. Is one instant of saying something in game really reportable? It just feels so bad to have teammates calling you autistic and terrible because you're having a bad game, and then to get banned afterwards. It really feels like if you do bad and say anything in chat, even if it's barely anything you can just straight up get banned if those 3 people flaming you all game report you. For context, this was the only game in the logs and the only instance of me saying something that could be considered toxic was after that 1 play.

Is there more chatlogs that I'm just not seeing? It'd be nice if a riot member could post them or explain why this was enough to get banned for :(