Mr. Vig's real gift
I think that Mr. Vig really wanted to donate the castle, but one of his unstated conditions was that he would play a large role in the day-to-day operations of the monastery. And, he probably wasn't even aware of this on a conscious level.
The film never really tells exactly what was his profession, but it seemed that he had an interest in theology, and he reasoned that if he donated the castle, he have some authority over the priests and nuns.
Mr. Vig wanted to do a truly 'good deed', but it was to be accepted on his terms without exception. I guess you could say, a bit of altruism mixed with spiritual vanity.
"Free to those that can afford it, very expensive to those that can't."