Asked how long it takes him to realise he has made a mistake, Carlsen answered, "The strange thing is that, usually when I make a bad move I see immediately why that is a bad move, and that happens to many strong players." He was at a loss to explain why this should be so, giving a partial explanation that one can see the position one move further ahead after moving.
I think the real reason has an emotional basis. While deciding on the next move we feel the pressure of time and the need to make a decision. We have to commit to a course of action. This gets the adrenaline going. After we make the move we sit back and relax. We look at the board again, this time more calmly, with no pressure to come up with anything. We broaden our view of the board, rather than focussing on the part that seems most important. Now it hits us that we overlooked something.