God, get over it people. No matter what you may think of them, people will still pirate software. We understand that you disagree with the practice.
Also, you are turning the "correlation does not equal causation" argument into the "Argument from Ignorance", which is a logical fallacy. Your assuming that since there may be other factors he is not taking into account (at least from our perspective), he is obviously wrong. All this proves is that no one knows the reason his sales increased, at absolute best.
Besides, this fits right into the idea that some people pirate before buying as a way to try a game out. It doesn't matter that it only costs $0.99. As someone before me stated, pirates will pirate anything.
Edit: This does not mean I agree or disagree with the guy. He is, however, in a better position than myself to judge such things in regards to his own software.