Once upon a time, at a bar. Brad Neely was drinking beer while "Harry Potter and the Sorcerers Stone" played on the television. The volume was turned down, so to amuse himself and his friends, Mr. Neely began doing commentary in that particular voice. It was so much fun he decided to do the whole movie and give it to the world. Most liked it, the end.
Basically what it comes down is that your bemusement is wasted. Why do flowers exist? Why do rainbows exist? What's the PURPOSE of making a wish on a shooting star, or the laughter of a baby?
Rainbows exist because one day Brad Neely was sitting in a bar and he saw an M&M commercial, and he thought "wow, M&M's sure have a lot of colors. I wonder what would happen if you took ALL the colors, ever, and glued them together, in the sky."