But that doesn't work if everyone actually knows the coin is just going down again.

In most crypto pumps that have ever happened, most people realize it is going back down again. They don't think that pumped coin sitting at market cap #432 or whatever is going to be the next Bitcoin. Or that some crazy copycat meme coin that suddenly shows up on the price gain or volume leaderboard is anything but a pump and dump. But many of these have happened and they still continue to happen. The psychology is just that buyers swept into the pump think they can ride it up even higher before the dump comes. Some are right, many are wrong.

Same exact thing with SBD. You can find old posts talking about SBD price gains and how it has farther to go and should be ridden up. People posting that at $5 on the way to $10 were right. Those posting it at $10 were wrong. (And you would think anyone posting on Steem would be more informed, but even informed doesn't imply rational or unwilling to engage in naked speculation, and even a little pumping of their own.)