Yitzyk, just because a man is independently wealthy does not necessarily mean that he should learn in kollel. Not everyone is suited to learn all day. It could be that his avoda is public service of some kind.
As for the general topic, my understanding is that being that a person has no way of knowing what was decreed for him or how much personal effort he must make he must do all that he can. After the fact if it does not work out he can say that Hashem said “No”.