Oooph. Yes, if you just looked at Henry VIII's marrying Katherine Howard, you might convince yourself that it was that Henry was an egotist, marrying a bride so much younger. He was far from alone in such a marriage. Charles Brandon, having lost his third wife (Henry's sister Mary), married their ward, an adolescent decades his junior. Among many others. Women marrying men decades their younger was less common for the obvious reason of children, but it was far from unknown. Especially when money (or other wealth) was involved.
Part of that was the likely causes of death. Childbirth tends to get overplayed in the discussion. All sorts of infectious diseases could carry you off. Also, accidents were both more common and more likely to be fatal. Both of which had this property: you were much less likely to live out your possible life span. The life expentency was what it was not because people died in their forties of old age, but because those who lived to be a hundred were counterbalanced by those who died in the forties -- and thirties, and twenties, and teens, and childhood. I've only heard stats from a study in colonial New England, where they concluded that if you divided up life into the first year, followed by every decade thereafter -- your chances of dying in each period were just about the same, no matter how old or young you were.
Which meant, of course, that a bright young apprentice, fifteen, marrying his master's widow in his thirties, or a heiress, fourteen, marrying a lord of fifty, were as likely to leave their spouse widowed as to be widowed themselves.
Not an easy thing to make palatable to the modern reader, especially since we tend to stint on the deaths.