well firs tof all, the israelites would have met the 7 nations, b/c they were int he areas the israelites were promised to get. plus the 7 nations were evil immoral people.
How do you know that god promised the land to the people?
How do you know that the other people were evil and immoral?
Is the answer , someone wrote it a long time ago so its true ?
Could it just be the rewritting of history by the victors of a conflict ?