Strange psychological phenomenon

I have just had very strange paired experiences in a couple of games; which I am at a loss to explain. Against two different opponents who were in no particular time pressure (for Bullet, admittedly) the following two positions arose. In both games my last move was ..., Ng6-e5. In neither game did White do anything about the main threat. In both game my next move was ..., NxQd3 and White resigned. One such oversight would be human and explicable: I have missed such things in Bullet myself. Two in such similar positions suggests there's some sort of explanation in the field of human psychology. Can anyone shed any light on why Black's main threat in such a position might go unnoticed? I can only think that the intention to gang up on the Pf5 creates some form of idee fixe.