He was so changed that he actually built a jail cell within one of Alexandria’s homes.
He’d gone from half-mad to full-zen, in large part because of the patient lessons from John Carroll Lynch’s short-lived Eastman.
It’s here that Morgan shifted his concept of survival and opened himself up to a similar form of rehabilitation from others (just as Eastman had done).
Morgan’s story seemed very weird at the time, but it’s now far more obvious that it was setting up the end game between Rick and Negan and the All-Out War arc on the way.