Yeah, they won because they made things easy imho. Lower barrier to entry === higher user base. I would contest your 'everyone and their uncle had a site' comment, though - for flash you still had to be 'in the know' or curious of how the flash games/animations were made, and then be inquisitve and resourceful enough to get yourself a 'copy' of your preferred flash ide, then figure out how to package/host/etc. Sites like livejournal/tumblr are more akin to what you are describing imo.