Why does Angel leave?

Lou Anne knew that they would divorce eventually, but did not expect him to leave her while she was pregnant. He claimed that it was because of his leg: he had been in a car accident in which his boot caught on the door frame, and he had to have his leg amputated. Angel, whose appearances in the novel are primarily recalled second-hand, is portrayed as an unstable and immature man bitter over his fate and unable to continue his relationship with a doting wife.