Stack Overflow has seen a substantial decline in traffic over the last year that appears to be accelerating. https://observablehq.com/@ayhanfuat/the-fall-of-stack-overflow
Don’t forget that Duck Duck Go is even worse at it now. It will literally change your results if you go back after clicking a link.
I think they’re trying to implement a sort of “smart prediction” thing, where it assumes that if you go back the link you clicked wasn’t relevant. And so it tries to remove closely related results. Which works the opposite if you get two results from the same page and you click the wrong one. Which makes looking up technical or programming related issues a nightmare.