unless they are legitimate fat fetishists, which is not common, they like the sense of security and comfort a fat man provides. a fat man is less likely to get attention from other women causing him to cheat, is less likely to pressure the woman to be thin and healthy, and is more likely to have poor self esteem making it easier for the woman to get away with more in the relationship without the fear of her man leaving her. it's like men who want gross 'femcel' gfs. they just want someone desperate and willing to keep their standards low so they don't have to do any self improvement