We would have expected that it would have been because God wanted him to do so. Think back just a few weeks to the portion of Lech L’cha where the Almighty tells Abraham to leave his homeland, and the patriarch obeys without question because a righteous person never puts his own advantage first.
Here it seems that Jacob’s motivation was not heavenly but earthly. Life with Laban was never easy and now it has become quite unbearable. True, when he tells his wives and family all this he does tack on a night-time dream in which God told him he could not stay, but the primary motive seems to be considerations of self.
Amongst the possible explanations we might suggest that though as a tzaddik Jacob is always guided by God, he cannot necessarily expect his wives and children to share (at least not yet) his own high level of belief and spirituality, and he needs to tailor his words to the thinking and priorities of his family. In that sense Jacob is acting the diplomat, achieving the same ends but carrying others with him for their own reasons of self-interest.
Another possibility is that having worked out in his own mind the need for departure, the patriarch has a restless night worrying about whether God would approve his project. Some time before dawn comes the response, “Go!” We presume that God could have said instead, “Live with your problem where you are! Stay put!” If this had been the Divine command, Jacob would have had no alternative but to remain and suffer.
In a sense it’s a parable of Jewish history – a dialogue that must often have occurred to the Jewish people when they were in agony and wanted out, and their reading of God’s will was to stay where they were and try and rise above their worries.