Why does Cronus rebel against Uranus?

In Greek mythology, Cronus did not rebel against Uranus, but rather castrated and overthrew him. The main reason for this act was Gaea, Cronus' mother. She was angry at Uranus because he had imprisoned his children, the Cyclopes and Hecatonchires, in Tartarus. Cronus, as the strongest of the Titans, was tricked by Gaea to ambush and emasculate Uranus.