I think it was a combination of staying on his meds and maybe just getting older. This article says:
Schizophrenia Recovery
Some people do recover “fully” from schizophrenia. Ten years after diagnosis:
- 50% of people with schizophrenia recover or improve to the point they can work and live on their own.
- 25% are better but need help from a strong support network to get by.
- 15% are not better. Most of these are in the hospital.