My father-in-law is like this. My mother-in-law is a controlling, manipulative cunt and he just lets her do whatever he wants because to him, it's easier than dealing with her temper tantrums if he tells her "no" or tries to stand up to her. She is absolutely horrible with finances, yet he let her control them even though they almost lost their house (and my husband had to bail them out...) because to him, that was preferable to stepping in, telling her she was no longer in charge of the money, and putting a stop to her frivolous spending. I think in any relationship, marriage or otherwise, once you establish a certain pattern (he caves in to all of her demands) it's incredibly hard to change it after a while, and some people would rather just let things continue as they are and be miserable in the long run than try to correct it and maybe be miserable in the short-term, but happy in the long run. And before you ask, yes, both of my husband's parents are fat.