There are no answers in Genesis

[Belacqua]

Why did theologians, for centuries, take the Genesis account literally?

Some did. Some didn't. 

I've already listed some who didn't. It wouldn't be possible to type out a complete list. 

Have you read any of the Cappadocian Fathers? Their knowledge of Greek philosophy tended to make them less interested in literal interpretations. 

Have you read any of the Jewish theologians who followed the Pardes system? They also felt that the literal reading was the least important. 

There are a lot of different Christians, so I'm sure if you look around you can find somebody who took it literally early on. I haven't read any.