I said "I think", not "I'm know that". See the difference? But it seems to me that people thought that the bible was true back then, and it's only since science debunked pretty much everything that the interpretations have changed.
How do you know that people thought the Bible was meant to be taken literally "back then"? Actually, what do you mean by "back then?"
For example, it wasn't until the late 1800s that someone decided he could calculate the age of the earth by counting generations listed. Some people latched onto this as a "fact." Many did not.
Before then, "day" and "generation" was a period of time that could vary widely.
Also, with King James we read that the flood covered the earth. Some decided this meant planet. Others did not. Why? Because the word King James translated as earth did not mean the entire planet. It meant earth--such as the earth outside in one's backyard.
There are some very old commentaries available, dating back centuries. Many (but not all Protestants) decided people did not need to study the Bible with a priest, rabbi, or scholar--that each person could interpret the Bible for him or herself. However...that did not begin until after 1500 years after Christ.
If you "think" something, isn't it better to have facts to back up your reasoning and opinion? Just because "some" people in the last five or six hundred years decided they could read the Bible and just know what the original authors intended, it does not follow that all people now--nor especially--people "back then" had the same opinion as literalists of today.