A lot of former politicians, military men, and even a former president from the United States left to side with the Confederate States of America for various reasons but the main reasons were the bounding sentiment and love for home country (your state) and also having deep-rooted families in that said state. So in short defending your family and friends of a particular area against a "foreign invader". Another reason is financial. either multi-business owning or large plantation owning. These were a large driving factor.