Human beings of all walks of life tend to overcompensate for what they perceive is lacking.
It doesn't matter whether it's actually lacking; when we have something we're insecure about we tend to overcompensate.

Is not just mtf's that do this, everyone does this in some way or another, just to varying degrees in varying ways in reaction to varying things.

I know I've caught myself overcompensating for my depression by behaving in a ridiculously cheerful manner... :/