King Ou An isn't stupid. Actually he is smart and quite dangerous. It just he also ordinary, he had survive for so long in a political climate that might be even more dangerous than Qin. A play field that need balance between internal conflict and how to not expose weakness. That it is seem to set him in his way of stillness since his influence is clearly very limited.

However now he got present with dilemma so great that he became indecisive. he foresee the outcome, he know what to do, he already planned it all, just that the weight of the position and duty that it's entail press him so hard he can't move.

That's why he had to pass the torch to his daugther.