Just got banned for winning a game! AMA

So I finish up a game of slayer. We win. I went 11 and 11. Not my best game, not my worst. After the game ends, I return to the matchmaking screen. It starts looking for a new team, then it says my connection was lost. It happens often when in the post game lobby, so I don’t think too much of it. When I clear the notification it says “the ban hammer strikes!”

Did I get banned for getting disconnected from the post game lobby? If so, why should it matter. I’m allowed to back out at that point anyway.