I tend to forget that a lot of newer members here don't realize that the merit system wasn't always a thing, that it's only been around for just over 3.5 years. OP already got his answer, so I won't repeat it. I'm sure if you go back to threads from 2010, you'll see that most of the members who posted have merit counts that represent exactly what was airdropped in Jan. 2018. And man, if you go back that far, it'll seem like the forum was a completely different one. There weren't signature campaigns back then, and I think the moderation was a lot less strict.
Some users don't even realise activity never used to be a thing either. It was vastly easier to rank up prior to it, because it was soley based on post count. I remember reaching a certain rank, potentially hero, but then activity was introduced, and I went back down to the rank below. I can't the exact ranks, but I believe it was Hero.