As I wrote in each scenario, AI has several plans. In this scenario, one of the plans is the escape of the observer. Apparently you came across this plan, if you play again it is not known whether it will be in the tower or not. This was the idea of these scenarios, the welds can happen differently, once you have to go straight to the monastery, another time try to get around it. You need to feel the situation and have a bit of luck just like in life.