Why did Aurangzeb depose Shah Jahan?

 The reasons for Shah Jahanís deposition are quite simple to look at. One could assume the rational by factoring in the support he harbored in favor of his eldest son Dara Shikoh. However the reality was a little different. It cannot be said with impunity what Aurangzeb desired to do with Shah Jahan after the battle of Samugarh. His main objective of defeating Dara had been fulfilled. He might have left Shah Jahan alone had Dara been captured at Samugarh. However Daraís flight kept the uncertainty looming over the destiny of the empire. There was no way Aurangzeb was going to turn back and leave at this point.

The mood in Agra after the Battle of Samugarh
Shah Jahanís Act of Diplomacy
Intercepted letter from Sha Jahan
Aurangzeb Confinement at Agra