I believe it all comes down to Point Guard play. As talented as he is, Judah Mintz is not a very natural or instinctive passer, facilitator or orchestrator - those aspects of his game still have much more room for development.
When your Point Guard is more of a scorer than a passer while still the team's primary ball handler, the fast break will suffer. When Judah is pushing the ball downhill, he's usually hellbent on scoring or getting to the line and passing seems to be more of an afterthought.
Bottom line: Mintz is a talented, gifted downhill scorer but he's not very good at leading and setting up his teammates in the traditional point guard sense - he's much more of a shoot-first COMBO or LEAD guard than a classic play-making POINT guard. And since he's the primary ball handler, SU's fastbreak suffers because of it.