They were mustard gassed in their homes, not starved. They were farmers living in the north, while Baghdad was in (from memory) central/South Iraq, so this weak minority would have had to trek through what would immediately become hostile terrain for miles. It's like you're asking British pastafarians to overthrow France. As to your second point, the same way a white minority ruled a black majority in South Africa. Through force, guns and it wasn't worth it for most black people. It was a dictatorship.