So in answer to your question of how was he allowed to be in ministry? Well no one probably knew for sure that he was engaged in a homosexual relationship until he told everyone.
I am not Catholic. But if he was in a 30-year long homosexual relationship, shouldn’t the parish priest or someone else have known about it? Who vets the people who are asked to participate in the ministry there? I know at our church, there is at least some effort to make sure anyone wanting to be involved in ministry is not living in open sin before they are allowed to participate in ministry. And we have almost 3000 members. Since we have 3 different services, there are many people I don’t know, but I know our pastoral staff checks out anyone who works in ministry.