This is something known as Low Priority Queue, and it's a punishment given to you because you went AFK/left too many games recently. Looking at your match history, there's a game where you played as Ashe that counted as a leave, and a game as Maokai which you obviously had dc'd from at some point in the game, and it was a ranked game no less, which does count against you more than a normal game does. Because you've been disrupting games by dc'ing, leaving, AFKing, etc., you have been put in the Low Priority Queue.
Now, if you been dc'ing because of something out of your control, don't think that you should be off the hook completely. Just because it's due to something out of your control, it's still your responsibility to make sure you have a stable connection and can play through an entire game before you queue up. If you're constantly getting dc'ed due to bugsplats/game crashes, then you should figure out how to fix the problem before playing another match, otherwise you'll likely just end up getting dc'ed again and ruin the game for 9 other players.