There are several things at play here. Having been very involved in parish finances in the past, I can tell you there is simply no other time to make financial appeals except during the homily. That is unfortunate, but it is a fact. After communion, during announcements, people do not want to sit through more than a few sentences. We tried before mass, and the simple fact is half the church fills up the last couple of minutes before Church starts, so you miss a lot of people.
I can further tell you that every priest I have ever met, hates to do it, does it reluctantly, and as rarely as possible. In this particular case, if it was a visiting priest, I assume he was travelling to various parishes to specifically raise funds for his apostolate, and the pastor allowed him to do so.