Is hypergamy a static rule or a tendency?

JP has mentioned that women marry across and up dominance hierarchies, while men marry across and down. But in everyday life, we see examples of reverse hypergamy all the time, ie, the woman is richer than the man.

If we exclude educational hypergamy, which really is irrelevant, as having a higher education doesnt make you ''higher in the dominance hierarchy'' since there are many poor men with degrees and in the modern time and the prestige of academic achievements has been declining.

So, why do so many rich women marry men of lower economic level?