The big theme in the Bible is that God keeps trying different stuff to get people to treat each other decently without canceling their free will. Some of these plans are not successful at all, others are somewhat successful.

One of these plans is that God picks out a tribe and decides to go very hands-on in their history while giving them special rules they have to they have to follow. The success of these people when they follow the rules, and their downfall when they don't, will serve to show everyone that God is real and we should listen to God when God says to treat other people decently.

God doesn't want to give these rules to everyone because he