Samoans are great and friendly people - at least all the ones I've known (which is quite a few) and I live in the city which has the highest Polynesian population in the world. They do have incredible genetics for muscularity and strength on average, but most of them are pretty tall (over 6 feet) and their large frames are more suited for the sports they are interested in, the main one being rugby.
Pretty much every Samoan guy I know has a lot of respect for the way bodybuilders look and for anyone who is built and / or strong. Tongans are actually a bit bigger than Samoans and Maoris are probably up there too, although there aren't many of them left who aren't of a mixed race / ethnicity. As someone observed, they like to eat, being as big as they are, not to mention bodybuilding couldn't hold a candle to rugby when it comes to popularity, acceptance and being an endeavor that's financially rewarding.
That and the fact that it's not easy to compete successfully in bodybuilding without a whole lot of knowledge and drugs, neither of which are easily accessible. Bodybuilding's anti-social aspect is probably a factor too.
