If they would have a serious problem with your content, they would not only de-index you, they would ban you.
But why they de-index stuff has various reasons. My best guess atm is, that no human was involved with de-indexing. Other than the trolls reporting your stuff for false reasons. Reasons that a human would have to check out. Even with 10% your sales volume probably would not cover the cost of staff looking at your stuff. At steam you have to pay to even enter their system. I believe it is 100 bucks. That keeps away all those pirated games and pays for staff to look at the game.
They should seriously consider having a thing like verified accounts. Whatever they are doing now, it is not working. At least I see lots of problems happening.