Michael needed the final recognition from the church itself to make himself and others believe that he truly had become an honest citizen.
Why? Michael wasn't particularly religious (and in books he wasn't religious at all) until Lamberto convinced him to confess and he considered himself irredeemable. He had to know that Church could become involved in extremely shady dealings.
No, I don't see it. Philanthropy, yes, I see how it would accomplish both these things, but recognition by the Church? In 1979? I don't see it.
Maybe it was a strategic move re: Immobiliare.
This actually happened in real life too with Joseph Profaci. Profaci ultimately failed in getting this recognition, but he almost got himself a knighthood.
But it happened in the 40-ties, IIRC - big difference. Also, Profaci was heavily involved in crime until his death and needed it as a "beard". He was very religious, too, however he managed to reconcile it with his life choices.
Michael in GF III seemed to be doing very well solely with legitimate business, since he was, presumably, a genuinely good businessman. Books suggested that as well.
