They had no real original content of their own, just worked solutions to homework problems they pulled from textbooks. They were good at SEO and would appear at the top. You clicked on it because it lied to you: showing you part of the content you wanted. Just enough for the search engine preview. That probably boosted them further, wasting more time by others tricked by the same fake results.

To see the rest of the answer, they wanted you to pay money and hope it was what you wanted. Who would subscribe to that other than students desperate for homework answers?

Then ChatGPT comes in without any of the scammy tactics. Sure, it's often wrong, but so are Chegg and Quora.