why did herman get demoted on chicago fire

Christopher Herrmann was demoted from captain to firefighter on Chicago Fire because he realized he did not want the responsibilities of becoming a chief or working in an administrative desk job. Throughout Season 13, Herrmann felt pressure from Chief Boden to step up and eventually lead, but his heart was not in it. He is fundamentally a "boots-on-the-ground" firefighter who prefers being actively involved in firehouse work rather than managing from behind a desk. In the season 13 finale, Herrmann voluntarily stepped down to allow his friend Mouch to become a lieutenant on Engine 51 and lead the team, feeling that Mouch deserved the opportunity and Herrmann was happy to be a regular firefighter again. This decision also came with a pay cut and some financial concerns for Herrmann, but he chose fulfillment over rank. Herrmann's demotion was more about his personal preference for his role and less about performance or failure.