Complex sentence: Mankowitz knew Saltzman casually from Broadway productions the two had been involved with and knew Saltzman held the rights to Bond, so he immediately offered to introduce the two men and arranged a meeting between the two the very next morning.
Split into simpler sentences: Mankowitz knew Saltzman casually from Broadway productions the two had been involved with, and knew Saltzman held the rights to Bond. He offered to introduce the two men and arranged a meeting for the next morning.