It allows them to have more children therefore more genes are passed on so it suits their selfish needs in a very animalistic sense. Although surely we should not be emulating the animal kingdom. Aren't we more sophisticated and considerate than that? I feel in this day and age we should have moved on and evolved.
I think that polygamy meets male interests because they get to have multiple wives to serve them. That means there are more women to satisfy the man's needs, someone to always cook him dinner and clean his house. Basically everything a man's wife does for him, he gets that multiplied in a polygamist relationship.
Polygamy is a tricky subject. I definitely do not think it meets male interests but I also do not believe it fully undermines them. As a whole I do not think it meets them though. People, males included have a vast array of sexual and social needs. Some people require polygamous or polyamorous relationships to fulfill that need.