Galante was a stronger personality and more business savvy than Rastelli.

You only have to look at how Massino was a Rastelli loyalist.

Under Rastelli's mentorship, Massino increased his own power. He played Rastelli like a fiddle in a way he wouldn't be able to do with a guy of Galante's insularity.

Look at the way Rastelli carried himself when he was on trial. The guy could barely stand up. He was a nervous wreck; not a firebrand like Galante.