Media doesn't have to be good to be popular. It only has to be entertaining.
The difference between JJK and KNY is that I never watched JJK but still got plenty of memes from it on my YouTube feed (e.g. "Nah, I'd win", Lobotomy Kaisen, Opp Stoppa Raga, "Stand Proud", "I alone am the Honoured One", "Imaginary Technique: Purple" etc.).
I have yet to see a single KNY meme appear on my feed. Which is strange because KNY was supposedly one of the most successful manga/anime series ever but it just doesn't seem to have garnered much of a lasting legacy.