could a big factor be that mormons stay married because half of every mormon marriage - the woman - is depending on her husband to choose to call her name so that she will be resurrected someday? That would tend to keep you from making him mad. Add community pressure, which is great.
LDS Apostle Erastus Snow preached the following on Sunday, Oct. 4, 1857:
Do the women, when they pray, remember their husbands?... Do you uphold your husband before God as your lord? “What!—my husband to be my lord?” I ask, Can you get into the celestial kingdom without him? Have any of you been there? You will remember that you never got into the celestial kingdom [during the temple ceremony] without the aid of your husband. If you did, it was because your husband was away, and some one had to act proxy for him. No woman will get into the celestial kingdom, except her husband receives her, if she is worthy to have a husband; and if not, somebody will receive her as a servant. (Journal of Discourses, vol. 5, p. 291)
never-the-less, staying married is a very good thing and mitt and his wife have done well in this.
1. LDS doctrine teaches ALL will be resurrected.
2. LDS doctrine teaches that the level of exaltation one achieves depends on their own personal worthiness, not because of the actions or choices of someone else, including their spouse.
While community pressure may be a significant factor, They "stay married" because that is how a mormon is defined. If you divorce, you're out. Saying Mormons have a high rate of staying married is like saying farmers have a high rate of agriculture. There are plenty of divorced ex-mormons who are not included in the statistics.