It is not the HOF writers and members. From what I have read and heard, Rose signed a contract that banned him from MLB for life.
Rose and Commissioner A. Bartlett Giamatti signed an agreement in which Rose agreed to a lifetime ban from baseball in return for the league not making a formal determination about whether or not he had bet on baseball.
He in theory is not even in consideration or on a ballot. Well his lifetime is now over. Be interesting to see where the HOF discussion goes next.