ESPN is motivated in part due to the dissolution of the Pac 12 that cost them their west coast footprint. They still have some west coast presence with the Pac 12 teams that joined the Big 12, but those rights are shared with Fox.
Stanford and Cal gives ESPN two west coast teams in the ACC where it has exclusive rights. Not the two most desirable west coast teams, but better than nothing.
Has anyone NOT figured out yet who is driving realignment?