Whats happening in the premier league..

The premier league has been awesome until this very end where all of a sudden things have gone parallel.. Its like a sorcerer did something.. At this very end all the big teams are loosing to the small teams..
It all started with Leicester city loosing to crystal palace by 5 goals to nil.. Den again Stoke City loosing to crystal palace again but the most surprising one is the case of Tottenham Hotspurs loosing to west brom.. If I was told it would happen I would surely argue to the last but........
CAN SOMEONE TELL ME WHATS HAPPENING TO PREMIER LEAGUE????