I imagine Sybok became obsessive and myopic, to the exclusion of other relationships. A workaholic in finding Sha Ka Ree. Angel was more pragmatic and simply moved on, i.e. did the more logical thing...I admit I'm curious why Angel isn't around in ST V.
Probably got tired of Sybok's constant ranting about Sha Ka Ree.
(srsly. I don't see Angel putting up with talk like that)

