> Unauthorized videos are taken down with vigilance, we see this happening to content creators all the time for no good reason. If these videos get the thumbs up to stay up, they're in cahoots with copyright holders somehow (most likely) or are deliberately ignored for some other reason. One think you'll notice is that not just corporate sponsored content is region-locked; sometimes "anonymous" user videos get region locked. That is not a coincidence.
This is all much less nefarious than you make it sound.
When a rights-holder finds their IP in a video, they have the option of how to proceed. They can choose to take the video down completely, run ads and receive all or a share of the revenue, etc.
If they choose to leave it up, it's almost always because they are receiving all of the revenue from the video now so they have no reason to take it down. There's no smokey back room deals going on here, this is just the rights enforcement tools provided by YouTube.
Rights-holders do not always hold global rights to content and if the video contains content from multiple rights-holders, there are several competing claims that all need to be resolved.
The reason the videos uploaded by users eventually end up resembling the videos uploaded by the rights-holder is because YouTube provides a mechanism for rights-holders to enforce the same restrictions they operate under on their content even when they weren't the ones to upload it.
Source: I work in a company that does this, though not directly on that side of the business.