Because a Bishop is the head of a diocese, not just one parish. The Bishop is sovereign in his diocese, and is able to exercise prudential judgement.
The Pope is sovereign in the diocese of Rome, and Vatican City. The Church is the laity, in conjunction with Bishops, supporting the Pope. The Bishops, in union with the Pope, provide authoritative teaching, guidance, and direction to their dioceses.
Thus, there may be an issue in one diocese, but not another, and is best handled by the local ordinary.
So, no, this isn’t a leadership issue, nor an apologetic for the Pope. Rather, it is the explanation of how leadership is exercised at the appropriate level of organization.
Since the mid-60s, seems to be a failed model.