Can I know everybody else's opinion on my 14 day suspension?

So i was playing a game yesterday, and it didnt go so well. Ammumu got executed when he was doing blu, which resulted in him going afk. our mid was also afk. This placed us in a 3v5, which in itself is already hard enough to win. However, i was being camped and everybody on our team was having an extremely rough game. Of course, we agreed to surrender at 15. By then, i had been trying my hardest, defending with my two team members. And we all know the season we're in is nigh impossible to make a comeback. However, the enemy yasuo was begging for a mastery mark, and i figured, everybody on my team had agreed to surrender, agreed to take this loss. None of us had hope of winning. I decided to help the enemy yasuo achieve what he wanted. After all, league is just a game right? The point of league is to have fun. At least somebody should enjoy this match. I helped yasuo receive his s, and i received a 14 day ban.

I ask you, what have i done wrong. I acknowledge that intentionally feeding is wrong, but in this situation, victory was impossible. I had actually tried in the beginning. This is also my first time actually helping the enemy. I did not flame, i did not accuse anyone, and all i did was try to make the best of the situation. I think we all know how painful it was trying to get the last mastery mark for lvl 7.

If anyone can help me i would appreciate it a lot. I have already talked with a rioter, and they refuse, saying that you just cant feed. I told him to look at it with a player's perspective, but he would only repeat "you cant feed" . Thank you all in advance.