Settling is different because usually someone has only a few things you don't find ideal but if the rest of the package is good then that's not a big problem - most people settle. The problem is when you have zero attraction to personality or looks. You just cannot force it. You will end up miserable and resentful.Marriage is physical and mental but society has put us in predicaments where it's financial as well which increases divorce and infidelity rates. You should never marry someone you're not attracted to.
I have no doubt that a woman can be attracted to a man that may not be her physical type.... but that’s my point, once you start losing traits that your woman is attracted too outside of the physical (status, money, resources etc), that attraction will fade and she’ll be looking elsewhere.
Relationships like this are completely transactional. Once the money is gone they jump ship like you said because there is nothing else they are attracted to.