Given how many people are alive in today's world it is completely natural that stuff like this is going to happen. Just as there is a person alive for any type of hobby you can imagine, so there is a person that can feed animals with all types of food you can imagine. There surely must be a person that feeds horses with donuts, so why not try to feed squirrels as well?
People used to picture squirrels eating nuts - that is their signature move, but this photo shatters that image for good. Now, every time you are going to think of squirrels, you are going to think of a large Dunkin' Donuts extra glazed one in their hands. Hopefully, the squirrel wasn't diabetic - that much sugar is surely going to cause it to go into shock!