But Haejin could have easily bought in Steem earlier in the summer and then took a few months to hatch his plan.

On a related note, I think the number of followers is unbelievable - literally. A significant part must be automated which is pointing in the direction of either:
-some brilliant long con
-opportunistic change of behaviour after initial succes

You can tell from who up votes him and how they up vote him that it is pretty unbelievable. A lot of accounts that circle all around Haejin, giving him 75% or more of their up votes, and some of his hard core followers also raping the reward pool and giving their 98k SP investment output basically just to themselves.