I live in a city area next to the end of where it got developed, there are several "colonies" of abandoned cats nearby. My mom used to take care of them, we ended up with 16 cats at home just from "emaciated rescues" that we managed to bring back to health (not all made it) and didn't manage to place somewhere else, about 20+ in a couple nearby colonies, some 40+ in some farther away ones... all the time working with a "capture, spay, release" program... and I got livid when she sent me a photo with 5 kittens in a box someone had left next to a dumpster, asking if she should take them home.

If you wanted kittens, I could find you so many kittens, that you wouldn't have the time to make videos of all of them.

What you really should be asking though, is: what did they do with the grown up cats?

A well fed and cared for house cat, can live 10-15 years. Where did those YouTubers put all those kittens, for the next 10+ years?