Well at the time I signed up, there was a large amount of top users all still very active and posting daily. By the time you had a meme hit page 1, there would be long comment threads and if it was your meme and you replied and upvoted to everyone’s comments, you would have potentially another 2-300 upvotes via comments on top of meme upvotes.
Back before I joined here, I can see that top comments on memes would get 100 upvotes sometimes. So clearly the site has lowered in popularity since say 4-5 years ago, hence harder to earn points.