Dirk is a super hard to understand character, but i think his main motivation was "get away from the people living their lives so i dont ruin them again" and that was twisted by his bro and cal parts to lead him towards villainy, which was in turn justified by dirk because "its all a story and im just on my villain ark" and "without me everyone would fade into obscurity" until he gaslights himself into believing its all for the greater good