When studying history, some might get the idea that a lot of historical incidents or developments were in a way inevitable. Because we know now that the Axis powers lost WWII, or that the Macedonian successor kingdoms lost against the Romans, it seems like that was just the way history had to unfurl. Yet, if it was obvious that the Axis powers would lose the war, they certainly wouldn't have started it. Or if the Macedonians knew the Romans would take over their kingdoms, they wouldn't have fought amongst themselves so much. Only in hindsight does it seems obvious what was happening. For the people alive during those times, it wasn't.
Nevertheless, when searching for explanations why the Allies won WWII, or why the Romans conquered Greece and the middle east, this hindsight bias plays an important role because it is precisely because we know what happened that we can try and come up with explanations why it did.
So, how do historians balance an unbiased view, 'through the lens of the historical people' so to speak, and an overarching view wherein they can think about the why-questions and come up with explanations for historical events?
The simplest way to look at it is that it depends on the question you’re looking to answer. Historians aren’t just interested in what happened, they’re also interested in why and how it happened. What were the underlying factors? Are there things we didn’t consider yet? Are there alternate views? Can we trust the sources we have? When and how did the understanding that we have of what happened become the dominant view, who propagated it, and why?
To give one example: the early Islamic conquests. The religious view is that they were spreading the righteous word of God and this helped them defeat the byzantines and Persians. Another view would be: Byzantium and Persia were weakened by a 6th century plague that decimated their populations; the plague had little affect in Arabia. They’d stopped paying off their tributary tribes in Arabia—the Ghassanids and Lakhmids—who were supposed to act as an early warning system for any trouble down in the peninsula. They were brought over to the side of the Muslims because they could be paid, and they had intel on the Persian and Byzantine military stationed in Syria and western Iran. Suddenly it’s not about divine fervor as much as it is that the Muslims had superior intel and were able to achieve complete surprise against what should have been a superior force. We can also work in questions about which side the peasantry supported, military tactics, etc.
A much more contemporary example: when I was doing my dissertation research, I was reading the Egyptian press during WWI, when there was discussion of the proposed Zionist settlement in Palestine. Granted, some of the pieces were hostile, but a surprising number of them were quite positive: Muslims and Jews are brothers, we’ve always lived side by side, there’s no reason this can’t work. I’ve had my students read these to remind them that where the Arab/Israeli conflict is now in 2020 was by no means inevitable. The question is how we got here, and that’s what we can examine as historians.