They find some technically hip, well known content and create a new channel with a very similar name as the originator. Create an exciting full screen ad for a crypto currency faucet scam, with price charts and crawls. "Live" stream the original content inset into the ad.
Here's one example: https://cryptoplayboys.blogspot.com/2021/11/spacex-scam-live...
Even if you report these things, they don't get removed very quickly. They're getting tons of views so why would YT care? The original content holder would care about being associated with them and should sue for defamation though.