Would there really be enough revenue to warrant doing this, considering 1) scraping and hosting that content requires some effort, 2) the content would (should?) be penalized for plagiarism so they would have very little traffic and 3) developers are probably the worst audience to try and monetize with ads due to the prevalence of ad blockers.

Most people who code are not developers.

Mine and my partners parents learned c (badly) at some point. Nearly everyone on the b2b customer support team at my last job could sling some js. A surprising number of marketers learn to wrangle some carousels/buttons/etc. vba script excel monster stories are prevalent.

These people are great to monetize. They are paid well and doing something they don't understand well.

I see them in search results often enough (sometimes even before the SO post they've scraped) that it seems to be working, and the search engines (both DDG and Google for me) haven't caught on.

> and the search engines haven't caught on.

Sure they have. They just don't care as long as they made their quick buck off of it.

Very little traffic, yet enough to be annoying?

The data is provided as a downloadable dump, so it's really just a basic read only CMS.