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It's not necessarily the rules either. Yamaha's factory 450 effort in the US was pathetic, and they had horrible results before Star Racing took over. I would bet a lot of money that Kawasaki is currently in a similar predicament with their 450 effort and they don't REALLY know the best way to set up the bike for their riders, in spite of what they tell the media. Some riders like Eli, Jett, and Roczen know how to set up a bike without the team's assistance. Chase clearly doesn't have that skill, so whatever base tune the team has for...

Different people running the teams for one thing. Problems/Success start at the top. Secondly, Different rules for different series. Kawasaki can run a bike with modified frame and engine cases in MXGP. Simultaneously, they can instruct Febvre and the team to tell the media they're running a stock frame/engine, and who's gonna interject and fact check that?

Who has the “master” footage of these mid-2000’s races at this point? Is there any hope to these being uploaded somewhere in their original resolution, or upscaled? It sucks going back to watch a season from say, 2011, and the quality per race varies so wildly due to them being different YouTube uploads from different accounts.

If you're interested, there's a great video explaining why this is the case. Long story short, the original footage was also "low quality" (480p) because it was meant to be broadcast live onto old school TVs. Expanding on the points made in the video, this low quality footage was then recorded to VHS using non-professional grade tape and non-professional level recording equipment. Then it was stored for a while, probably in suboptimal conditions. Then it was uploaded to YouTube. The footage began it's life at 480p, then took a beating for a few years.

Not 20 years ago, but check the quality of this: https://www.youtube.com/watch?v=O9KGZOSDLRo Much much much better than todays trash broadcast!