Yep, the activity of the platform is clearly marked by the price of the Steem, I suppose this is due to the reason you mentioned, many people think only in the immediate future and not in the long term, keep in mind that the Steem being a Crypto is constantly subject to a change of value, the "hopes" in the platform can also have something to do, just as there are many people who believe that a platform like Steemit is the Future, there are many who do not see it, by X or Y reason.

Of course also a psychological effect style: "I'm earning less than before" or "I'm not earning much per post" would make people have less desire to post, while if they see "high numbers" or that they are earning an amount that they consider decent would increase or help maintain that desire xD.