New poster here -i just read a couple of comments saying they were surprised they got married and asking what Ben finds intriguing and I am here to offer my 2 cents on this - I think Ben simply likes control.
He is a successful man and from his interviews he said that what he liked about going to the gym was that it gave him structure and he thought it could apply it to other areas of his life. In my opinion, that's also the appeal of Robin, like she literally flew across the globe to be a house wife, she is completely depending on Ben not only economically but also emotionally (her family, till her brother moved, was about a 12 hours flight away so realistically that's all she had). I don't know if I explained it very well, and just to clarify, I am not saying that every family/couple having one person working or earning significantly more than the other has a power imbalance per se, I am just saying this seems to be the case for them and to me that is the appeal Ben sees in the relationship.