Plenty of people master more than one domain. It's actually easier when the knowledge is more accessibly distributed in more generalised form, so you don't have to find out how to build stone vaults that don't collapse by trial and error

Ancient civilizations were full of laws people didn't control and property they didn't own, enforced by weapons they had no idea how to make imported from regions they knew nothing of and would have no opportunity to ever visit. And you didn't really understand the priest's explanation for why the gods had determined your infant sons deserved to die any better than the average person nowadays understands the antibiotics that could have enabled them not to die...