one of the arguments he would make to Ben Olson was that it was easier to be a missionary on a team and at a school where you would be one of the few members of the church. Whereas if you are at BYU the amount of missionary work you could do is a bit limited because most everyone you are surrounded with are also members of the church.
Who knows how much stock Olson put into those comments, but knowing him and it wouldn't surprise me if he valued something like that.
Also keep in mind that when I served around him Reed White (Max Hall's cousin who was a walk on WR at BYU) was also in our zone (and Olson was Zone Leader) so it's not like the only voice in his ear was telling him to not return to BYU.