Rutgers is also attractive to the Big Ten because of Penn State. Since joining the Big Ten, Penn State has been alone at the far eastern boundry of the conference. It would be beneficial to Penn State to have Rutgers, Maryland, or Syracuse (yuk) join the Big Ten.
There are also enough Alumni from the Big Ten schools living in Philadelphia, New York City and New Jersey to ensure that every Rutgers home game is sold out. Michigan, Northwestern, Ohio State and others would benefit from having fundraising events with their alumni that are tied in with football games at Rutgers.
It is about the money, and there are plenty of different ways to get it.