The initial success of youtube depended on three things:
High speed internet to become the norm
The use of Flash as a video player that could be embedded in a web page and it would just work.
Footing the bandwidth bills so that video creators didn't pay them themselves.
To get an earlier YouTube, you need to have faster and earlier adoption of high speed internet, AND you either need macromedia/adobe to add video playback earlier.
an earlier HTML5 is also a possibility, but likely a non-starter because at the time, everybody was using IE6, which Microsoft was just sitting on and doing no development on.
Prior to google video in 2004 and youtube in 2005, watching video content online was done by downloading actual files and then playing them back locally. And any video content creator would usually have to self host their files, and would have skyrocketing bandwidth costs if they got popular. YouTube footing that bill removed a huge barrier to entry.