The Bible is a very warts and all account.
It basically gives us what happens without going into detail as to the why's and wherefores.
Are all the possibilities to be taken in account?
The nations around them were known to be very immoral where they suffering from the usual illness that go with immoral lifestyles on a whole nation?
Did the nations take drugs that were in common use then?
Where there genetic issues with certain tribes that would have been detrimental to interbreeding? The phillistines were known to be unusually tall.
How would the israelites have treated them? Virgins they could marry and children they could intergrate and so would be taken care of but if others survived would the people simply have let them die slow deaths and starvation due to lack of resources then?
If allowed to live would the nations have constantly attacked the israelites? The constant attacks Israel was under then anyway shows this was a fact of daily life?
What attrocities had these already commited against Israel? Could God make them look after people that had killed israelite women and children without seeking revenge?
We know the tribes around the israelites were extremely violent, aggressive, immoral, into child sacrifice (Baal worshipers used to have burning pits that they suspending their own children above then drop them to there deaths in them to appease their God baal) how could they be intergrated?
How could Jehovah minimise the influence of those nations? We know Josiah was shocked at how much the israelites had strayed from the law when he became king?
When nations showed an ability to respect Israel they were spared.
Could God force Jews to be less violent without effecting freewill?
The speculations are endless but just putting a negative spin as the majority are doing on this thread is simply unrealistic and armchair moralising. Do we do better when we are far removed from the attrocities? When the governments you voted in do attrocities to other nations away from your eyes?
We have had Jesus's message of peace for 2000 years and yet we still think war and death are the answer! You may argue but we are imperfect humans but I say back that that is all God had to deal with. He had imperfect cloth he simply couldn't make peaceful he even sent his son with a message of peace and we killed him.
I think the Hebrew laws for the Jews covered a particularily violent and aggressive time period and the people needed preparing to be able to accept a more peaceful message from the messiah and even then they still killed him because of their violent tendencies.