That is a tall order for several reasons.
Philosophy as an academia is closer to a system of process than a system of belief, and that is even though philosophy does not follow the same process chain that other sciences use there is plenty of similarity on getting from an an observation or question to a theory or conclusion. What that means is the very nature of the age old question or an alternate question tends to challenge the beliefs people hold from whatever faith they subscribe to. Historically speaking, that is usually not very peaceful.
The age old questions on is there a God (or Gods) and what is God (or Gods) suggests filling a human need to explain something. The theistic argument to these aged old questions are based on another chain of thought. Because there is observable and objective moral reasoning, and a God (or Gods) would provide the best explanation for that moral reasoning being an overarching authority handing that to us, therefor we would not have that moral reasoning without a God (or Gods.) Again, the moral argument that we would not have them without a God (or Gods.)
So, let's change the question to... say... "why do we need a God (or Gods) to tell us what is right and wrong?"
The immediate impact is upsetting everyone in the room who subscribes to a system of belief that holds as truth where they derive moral reasoning.
And one of the things we cannot discount in any regard is the period of human evolution where all these systems of belief came from nor can we ignore that what we call the emergence of modern science was over 1000 years later. Thought, question, and philosophy all took their own paths across multiple periods of human history of course but when looking back to the bronze age there was no such thing as a system of process, no such thing as educated public, and no such thing as a search for answers *without* a system of belief. And that last point is why it became such a force of human history that we still see its properties today.
The age old question ended up giving humanity wide ranging interpretations on the existence of deity, what the nature of deity is, and ultimately what is the source for moral authority. Even though this ultimately lead to enough conflict and loss of life damaging what they thought was being answered. Ironically, moral authority ended up becoming a reason to divide and ultimately take life. On top of that the earliest systems of governance and law predate monotheism by 1000's of years, yet we still see humanity clinging to some of those systems of belief from monotheism today literally answering the age old question the exact same way. Way back then, way before monotheism humanity could objectively design law. Let's not kill one another, steal things, what have you. The concept of moral reasoning predates monotheism yet now it appears monotheism is corner to moral reasoning... let that sink in.
You bet we asked the wrong questions, and on this side of the emergence of modern science we still do.