As competitive and accomplished as Mullin is, I can only think that he'd take this job if he really believed he could be successful here.
Yes, the lack of coaching is a knock against him. This is where Danny Hurley gets the nod. However, if Mullin's smart, he surrounds himself with a top recruiter and X's & O's asst on his staff.
Also, I'm sure that Mullin wants to get a feel for the administration at SJU and make sure they're fully committed to fielding a top 25 level hoops program, financially as well as making sure kids can qualify.
I don't believe that the admin that Lavin was working under for most of his tenure was truly committed to supporting a big time, national level college hoops team. The past admin. seemed like they were fine with a competitive team who was still considered major in the NY area, but not nationally.
Under Mullin, the admin's vision and support must be much more wide reaching and they have to think way bigger in terms of financial backing if they want this program to be a legit top 25 team annually.