I just replied to a similar thread - so will just copy (with a little editing) what I posted there.
When God called the OT people to be His chosen people, He established not only a religion, but also a nation. The laws He decreed encompassed religion, health, civil government, everything. The laws you cite would fall under the judicial aspect. Unlike our democracy that insists on separation of state and religion, with the Jews, the two were welded together. What harmed the religion, harmed the nation and vice versa.
When Jesus came, the kingdom He founded was the universal kingdom of God (Church)- a religion, but not a nation. The members of this kingdom were to go everywhere and be leaven within the existing nations. Hence, the only “laws” retained from OT were the moral laws. (To these were added Jesus further moral teachings and doctrine, and His instruction on the hierarchical structure of this kingdom, His Church.) Old Covenant religious ritual laws no longer applied since, with the New Covenant, there was a new priesthood and a new sacrifice and ritual worship. Other national and judicial laws were no longer applicable since Christianity was not a nation.
You can usually tell how threatening a certain action was to this purpose of God by the severity of the penalty He decreed. What could prove fatal to the establishment of this religion/nation - where His truth could be taught, upheld and practiced - was likely to deserve capital punishment. (Keep in mind also the lack of prison facilities when the nation is rural, small, etc. When the laws were originally given, the Jews were still nomadic, traveling thru the desert.)
Acts that God considered a serious threat included:
Living side by side with pagans (hence the expelling or killing of pagans when the Jews conquered a land);
Jews who adopted pagan beliefs and practices;
Adultery (stable family life critical)
Murder
There are probably more; but if you examine them you understand why there needed to be a severe punishment if a Godly nation was to be “born” and survive in the midst of a pagan world. (An analogy in my mind is that the years from Abraham to Moses constituted the pregnancy; from Moses to Jesus, birth to adulthood; Christianity, adulthood.)
Nita