Mostly I did YTP type stuff, such as finding music videos, then finding another version sung by the other gender and dubbed the audio over, and uploading it because I thought it was really funny. I'd probably get hammered so bad if I did it today with the current copyrite situation on Youtube.
Made a few amateur sketch videos.
And also uploaded cool video game clips and tricks, before anybody was really thinking about trying to make a name in the gaming part of youtube. I had a livestream that I'd get 300-800 people at once, but wasn't able to keep up with it and honestly didn't think much of it at the time. It was more like it was just other people interested in the game that wanted to see higher ranked play, not some sort of popularity contest like it is today where every channel and stream wants to be "famous". (I was probably wrong about the situation but that's how I viewed it at the time.) The only way I knew how to make money from it was by giving lessons for like $10 an hour. XD
I guess the biggest "why" was to troll around and be funny. When tag spamming, auto-refreshers, and misleading thumbnails ruled the world.