I’m going to say it’s because the Church is an institution, and institutions naturally prioritise protecting the interests of the institution and its leadership. This is by no means unique to the Catholic Church. We see it in virtually every institutional setting in which sexual abuse has occurred. Indeed, in the UK currently we have an inquiry that is addressing institutional failings in addressing child sexual abuse, including churches, schools, prisons, local authorities, and central government.
For example, it is now known that the late Sir Cyril Smith, a sometime mayor of Rochdale and for twenty years the town’s MP, was a sadistic and prolific paedophile. However, he was seemingly protected by various institutions, including the police, MI5, and prosecutors, because of his public position, in particular because as Liberal Party chief whip in the House of Commons he would have played a key role had the Liberal Party been called upon to enter a coalition government.
The Catholic Church has finally come to the realisation that protecting abusers within its ranks is actually counterproductive, as the cover-up does more harm to institutional reputation than the abuse itself. Sadly, there are other institutions that have no yet caught up.