riot why did i take 20min ban if i just went afk for 5 minutes and came back?

A 20 minute Leaverbuster penalty is the highest it can give out. This means that you have a history of leaving/afking in games. Until you can play 5 matchmade games without leaving and/or afking you will continue to recieve LB penalties and stay in the low priority queue.

"I just went afk".............you answer your own question WITHIN the question.

Because it's supposed to be a deterrent.

https://youtu.be/ZJlF3xcYDw8

I just "afk for 5 mins" okay you are not exempt from the rules

Because you're not allowed to just afk for 5 minutes?

Five minutes is a LOT. You're not supposed to AFK at all.

Shit happens in life, but if you're getting a 20-minute penalty, you've been AFK for much more than a standard amount of unforeseen excuses. You gotta complete the matches you start, from beginning to end.

Because AFKing ruins the game for 9 other people, especially when you do it for such a long period.

Cos you've AFKed alot in the past, getting at least a 10 min leaver buster penalty and didn't play enough games for it to drop a punishment tier.

5 mins in an average 20 minute game...ok.

Because you went afk?