Do you think this is not normal?
There is no regular addition of content to FAF. Therefore, the loss of the audience is quite a logical phenomenon in such situations.
I am wrong? So look at other popular projects. Let's take Dota for example. Take a look at the Dota 2 online chart on Steam Charts on the first day of the Battle Pass release. Online is growing exponentially.
Answer the question, how much will online games like CS:GO and Dota drop if all battle passes and in-game cosmetics are removed?
Many play only for rewards such as in-game cosmetics.
I think it's foolish to be surprised at the loss of an audience until you find a way to regularly add content to FAF.