But there is much we know about who and when wrote the various books of the Bible, and we have lots of archaeological evidence about what was happening in the area of north Egypt and Canaan for that entire duration. And for example we know with high confidence that the Book of Exodus, the Book of Joshua, and the Book of Judges were written hundreds of years after the events that they purport to describe - so they aren't very trustworthy sources to begin with, for those of us who don't presuppose divine authorship.

Note also that atheists, whether scholars or not, have no particular bias against the historicity of the non-miraculous elements of the Bible. The general narrative of the story of the Book of Exodus could be explained in naturalistic terms, so it isn't dismissed outright by atheists the way, say, the Book of Genesis is. Moses could well have been some historical semitic leader that led a group of semitic slaves from captivity in Egypt up into freedom in Canaan, perhaps in the midst of a series of calamities hitting Egypt that allowed for their escape in the first place. That's why many serious scholars have looked for signs of these events, in many forms of historical sources - they simply didn't find any.

Contrast this to the story from the Book of Kings. Again, atheists will generally dismiss the story of the fire from the sky and the other miracles out of hand - but when they went and looked for evidence of a King Ahab and a religious leader Elijah, they did actually find it, and so they have no problem in attesting that these were real people who really lived.

In relation to the Book of Joshua - while it's true that Jericho exists as a city, and seems to have indeed existed at the right times to match the accounts, other parts of the narrative do not fit. In particular, the city of Ai was abandoned much earlier than any possible time for the narrative of the conquest (it was abandoned in 2400 BCE) and it wasn't re-settled until much later when a village was founded there during the Iron Age. So Jericho - maybe; Ai - no. Beyond this, there is simply no evidence to suggest that early Jewish settlements were conquered from "the Philistines" - the evidence suggests much more so that they were simply peacefully founded by Jewish people (that is, people who spoke Hebrew, followed Jewish dietary practices, and worshiped Yahweh).