Here is why Jakob's fear was so great. Targum Pseudo-Jonathan gives the reason the plain Hebrew only hints at: he was greatly afraid, because for twenty years he had not been mindful of the glory of his father (Genesis 32:8).
Twenty years in Laban's house. Twenty years without visiting Isaac. Twenty years without the Fifth Commandment's daily weight upon him. Now, at the edge of Canaan, with Esau thundering toward him in arms, Jakob realized that he had neglected the father whose blessing had started the whole chain of events.
His anxiety was not just strategic. It was moral. He divided his people, his sheep, his oxen, and his camels into three troops — one portion for Leah, one for Rahel, and one more in reserve. But the real division was internal. He was measuring himself against the duty he had not kept.
The Maggid teaches: the fear that arrives at the border of your homecoming is often not about your enemies. It is about the parents you did not honor while you were gone. Jakob split his camp on the outside because something had already split on the inside, and twenty years of silence toward Isaac had finally caught up with him.