It appears they got engaged 3 years before the eventual $90M accident even happened. So by the time they actually wed, they had to believe it was all about love, which I have no doubts that it was. However as tough as marriage can be, that amount of money can certainly affect people in strange ways.
Looking deeper: At around 40, he should never taken a then-20-year old seriously. The likelihood of her being the same woman at 30 and beyond was slim. Further, he had some money then, so that really alters the lens in which a very young lady views a older man. Motives should have been questioned.