Hi, I dont know much about how the tiktok algorithm works, can anyone explain why my reach fell off a cliff?

The only thing I can think of is that I recently pinned a promotional post. Could that be it? Am I not supposed to do that? Otherwise, my most recent drawing is under the same tags, same general content, and not to wet my own whistle but same quality too. If it got a 10th of the views I wouldn’t be making this post but obviously something is up here to go from 120k to 90