Because he's definitely high!
The stunt involved Red Bull skydiver Paul Steiner transferring between two high-flying gliders, which is pretty crazy, but my favourite tidbit related to this story was found in the comments section: "Oh PLEEEEZE!!.... Seriously, anybody could have done this." Sure thing! Evidently the commenter didn't bother to look beyond the opening photo to the one below:
via Chaz Hutton's tumblr. Check it out, that blog is chock full of gold!