Complex sentence: Dellacroce and many of his supporters were angered with Gambino's choice; although Castellano had been a major earner for the family for many years, Dellacroce and others saw him as a businessman rather than a gangster.
Split into simpler sentences: Dellacroce and many of his supporters were angered with Gambino's choice. Although Castellano had been a major earner for the family for many years, Dellacroce and others saw him as a businessman rather than a gangster.