Rehoboam made a bad decision, but it was really his father Solomon's actions that divided the kingdom. He forsook the one true God and chased after other "gods," he neglected to serve the people and instead forced them to work harder, and he was focused on himself, as reflected in his accumulation of wives, gold, and horses in direct disobedience to God's counsel. His son Rehoboam was merely living out the consequence of those decisions and actions.