Vincent Mangano was a Maranzano guy. He was named boss by Maranzano while Frank Scalice was demoted. Over the years he became complacent, was too much in the old ways for the young members of the family, and that complacency made him a slouch.
Look like there's a trend; Old school bosses were never really respected by the young guys. Look at the cases of Joe Profaci; John Stanfa; Vincent Mangano; Angelo Bruno.