From a sociological perspective, they likely didn't base their decisions on exactly the same thing we do, because they were socialized in completely different environments. Of course, this gets stretched out and exaggerated (like in the examples you provided) buts it's hard for people to simultaneously not judge the past by taking socialization into account, and then also acknowledge that those people were essentially the same as people living now.

Part of it is that sources reflecting the experience of the majority of people are often either unavailable or poorly known. Thus elite intellectual production comes to stand in for everybody, which would be completely absurd if we applied it to more recent times. ("The Greeks believed ... [summary of Aristotle, a highly original and idiosyncratic thinker, follows].")

This is a tension in history. Let's take the example of the Egyptians.

There isn't much land to inhabit in Egypt. So modern Egypt is essentially built on top of ancient Egypt, with the exception of Egyptian tombs and temples. (this is massively oversimplifying) This is why egyptian archaeology is the archaeology of funerals, essentially, and this leads to a very skewed view of Egypt. Similar gaps in our studies of ancient cultures, or simply what gets discovered first, can totally color our view of peoples who probably didn't have such a skewed worldview.

On the other hand, the Egyptians had some views that we today would consider very odd. They thought, in a particular way, that words and images had a lot of power. The images of grave goods you find in tomb paintings were literally believed to be brought to the deceased in the afterlife. Akenhaten was never spoken of again because not speaking of him and wiping out his name had a lot of power for them. So they did base their decisions on something different than we do.

In some ways, this isn't any different than today. Different cultures have different things they consider important. This is a major component of sociology and anthropology.

Peter Brown had a good article recently that dealt heavily with the differences between ancient and modern thinking, it opens with this:

"One of the most lasting delights and challenges of the study of the ancient world, and of the Roman Empire in particular, is the tension between familiarity and strangeness that characterizes our many approaches to it. It is like a great building, visible from far away, at the end of a straight road that cuts across what seems to be a level plain. Only when we draw near are we brought up sharp, on the edge of a great canyon, invisible from the road, that cuts its way between us and the monument we seek. We realize that we are looking at this world from across a sheer, silent drop of two thousand years."

The whole article is good if you're interested. Rome: Sex & Freedom