The monster was stunned by the sight of its own arms on the floor. It never occurred to it that someone would be able to deal this much damage, this much pain, to it. Looking at its opponents, it never realized that someone as insignificant as a human being can be a threat t its existence. For the first time ever, the monster felt disturbed. The monster never imagined that it would be subjected to this feeling called "fear".
Fear for its life.
Fear for the freedom that it just acquired would be taken away just as fast as it came.
Fear for the unknown, the uncertainty of the things to happen if this keeps up.
All of these thoughts are alien to the monster. It never had the time, nor the capacity to think about these things. It was "fear" that made it realize this thing. Fear was the fuel that ignited this evolutionary pace on it.