This is quite true. For example, archeology shows that the cities of Canaan were not conquered in a rapid military campaign (Joshua). It shows the cities collapsed from internal rebellions and over a time span of centuries.<quoted text>
Your theory would mean that because London, England exists then Harry Potter books are documentaries.
Note, there is little archeological evidence supporting a single thing in the Bible other than some place and people names. In fact the evidence often contradicts what the Bible says.
Example, "Nazareth" is not mentioned outside the Gospel of Luke until 300 years after Jesus died. It also places the writing of (the current iteration of) Luke as being written centuries after Jesus and Paul (and any 'Luke' of the time) were long dead.
Imagine a copy of the Declaration of Independence that refereed to the Lunar landining . Would you believe it was written in 1776 ?
And Israeli archeologists went on a serious hunt for evidence of Moses and the Exodus. They came up empty...competely...despite the Bible telling them right where to look. Their conclusion was that Moses was a mythological figure, not historical.
And the archeological evidence is that the Israelites were never slaves in Egypt. In fact were never in Egypt as slaves or not. The evidence indicates that the Israelites were situated in Canaan as a small, poor hill tribe. With the collapse of the Canaanite civilization, the Israelites moved to fill the power vacuum.