In the 90's and 00's there was a photographic movement to take photographs with more depth using more hand and arm movement to make more dynamic images. Some say it came from comic book artists and others say it started as everyone doing the double thumb and index finger as a ergatz frame gide of what you were about to film, but this time you were the subject.
Anyways it got popular so people with cheap cameras and phone cameras started propping them up and trying to do some of it and most of the time they didn't have enough time to get their hands right. So they started to take all these pictures of themselves with weird hands and people started doing it on purpose, and then photographers picked up on the trend.