App store ranking is kind of irrelevant, it favors new rising platforms, and underestimates an existing platform with a consolidated user base.

The expected trend varies depending on the stage in the curve. Threads is at the size were a positive trend should be exponential. Once you've fully expanded, a positive trend would be a very tiny growth as you've already captured the entire market.

App Store ranking isn't entire organic - can be juiced with ads.