Making money on YouTube with other people’s content is certainly possible, though, as you might expect, there are ethical considerations depending on how you go about it.
If you just re-upload someone else’s content wholesale, without any kind of modification, and pass it off as your own, there is no question that it is wrong in every sense of the word, including YouTube’s rules and guidelines.
So, not only would you be doing something generally unpleasant, but you would also likely fall afoul of YouTube’s policies, and lose any monetary gain you might have had.
That being said, there are ways to make money using other people’s content on YouTube that are entirely within YouTube’s terms, and you can do it in ways that won’t have the YouTubers whose content you are using wishing ill fortune on you.
There isn’t much more to say about this that we didn’t cover in the intro, but just to reiterate; taking another YouTuber’s content and re-uploading without their permission has very little going for it as a money-making tactic.