Same. I think what happened is that the early users answered all the most frequently occurring questions, and the questions honestly haven't changed much. I think my most popular answer is like how to diff with git. People are using git even more than they were when SO started, so it gets upvoted regularly.

Same. “Top N%” looks to just use score, and momentum on old answers is a big deal. I’m top 0.24%, with my score having increased by about 50% (25,000) in the last 3½ years (as far as their little chart shows), overwhelmingly because of momentum on old answers from 2010–2015—for during that time I’ve only made a handful of edits, three question, and six answers, three of which were for my own three questions.