Google has massive swing; there’s a whole industry around getting Google to prefer your low quality crap nobody wants to see over others’ low quality crap nobody wants to see.
If Google has finally figured out a metric to measure “helpfulness” of a website and punishes unhelpful websites, a bunch of dogshit that would have otherwise gotten top spots may have been banished to page 2.
Reddit results would naturally creep up because of that (and therefore get a lot more clicks), even if they didn’t change at all.