As I and others have pointed out, Cameo is not the copyright holder. That would be the Talent User, in this case, George Santos.
Here’s how this works, basically. The Talent User (Santos) in making a video to fill a request, grants a limited license to use the video to the individual making the request for their own personal use. In this case, it was probably a throwaway account some Tonight Show producer or intern created just for this bit. Which means the Tonight Show and Jimmy Kimmel almost certainly did not have a license to use the video. However, they may have a defense, which I mentioned earlier. They could argue that it’s fair use. That involves an analysis of four factors. It can get complicated, but those are basically (1) the nature of the original work (creative works get more protection that purely factual works like, say, a phone book----this weighs in favor of Santos here), (2) the amount of the original work (it looks like they used the whole thing—this is in favor of Santos), (3) the purpose and character of the use (“transformative” is the word often used, in this case, the purpose is comedy, maybe slightly satiric comedy, but I wouldn’t call it satire or parody which would help the Tonight Show’s case----still, I’d say this weighs slightly in favor of the Tonight Show, although it would help if it weren’t a commercial use, which it is), and (4) the effect on the potential market for the original work (this probably saves the Tonight Show’s bacon…there isn’t a market for the original Cameo video…it was a one off made for a specific request…it’s not like Santos was going to be able to make money off that video----this weighs really strongly in favor of the Tonight Show). Those four factors aren’t weighted equally. Each case is evaluated on its own. Generally, however, factors 3 and 4 in my list are the most important. And here, because there’s no market for that video that Santos made, the Tonight Show’s use of it didn’t harm Santos’s ability to profit from that video. Maybe he could argue that it hurt his overall marketability on Cameo, but (a) that’s not really relevant to the copyright infringement, and (b) I’d be willing to bet he got more business after this, not less. So I’m revising my earlier statement. Santos has a case, but I think it’s weak.