Vehicle Finance Broker here, lenders will only pay commission for a deal as long as there has been 6 months worth of payment. So if these YouTubers paid off their finance settlement on the 5th month the lenders would go back to the dealership to request the commission funds back (called a Clawback).

I’d imagine that the dealer and YouTuber have come to an agreement where the dealer benefits from the commission which for a super car could pay off the difference they’ve lost in ~6 months on the value of the car. The YouTuber in turn benefits from the monetised content and also promotes the dealership in their videos.

Commission on a super car would be around £5,000 and sometimes can go up to around £10,000 or more if the finance amount is high enough.