According to this Jewish Historical sit, they just didn’t want to: (
myjewishlearning.com)
I’m also calling
@meltzerboy to weigh in, as he will know the answer:
The Death Penalty in the Torah
The Torah imposes a penalty of death for a range of misdeeds. These include ritual infractions, such as violating the Sabbath, worshiping idols and cursing God; sexual sins, including incest, adultery, anal sex between men and bestiality; and various criminal acts, including murder, kidnapping and giving false testimony in a capital case. In one particularly challenging biblical passage (Deuteronomy 18-21), the Torah imposes a penalty of death by stoning in the case of a “wayward son” who does not heed his parents’ discipline. (The Talmud states that there never actually was a wayward son nor will there ever be one and that the Torah mentions it merely so it should be studied.) Stoning is the most common method of execution described in the Torah, prescribed not only in the case of the rebellious child, but also for murder, blasphemy, breaking the Sabbath and idolatry. The Torah specifies that a person may be put to death only on the testimony of two witnesses — never by one alone — and that the witnesses who testified must be the first to lay their hands on the accused to kill him. Death by fire is mandated for a number of sexual sins, mainly various forms of incest.
The Death Penalty in the Talmud
The rabbis of the Talmud discussed the legal requirements of capital punishment at great length, establishing significant barriers that made such a sentence extremely difficult to carry out. According to the Mishnah, capital cases had to be decided by a Sanhedrin of 23 judges. If the conviction in a capital case was unanimous, the accused was acquitted. Perhaps most onerous of all, the offense had to be witnessed by two people who warned the perpetrator immediately prior to committing the act that it was a capital offense. Such stringencies are often understood to account for the famous Mishnah passage that states that if a Sanhedrin executed one person in seven years, it was considered destructive. Rabbi Elazar Ben Azariah objects that the standard is actually once in 70 years, and Rabbis Tarfon and Akiva say that had they served on the court, no one would have ever been executed.
However, some scholars, such as Rabbi Louis Jacobs in The Jewish Religion: A Companion, have noted that the power of Jewish courts to impose a death sentence was ended by the Romans sometime in the first century of the Common Era, and as a result the Talmudic discussions of the matter, including their imposition of stringent rules of evidence in capital cases, should be understood as purely theoretical — not as practical guidance for how such cases should actually be adjudicated. Jacobs also pointed to passages in the Talmud and elsewhere that permit extrajudicial execution in certain circumstances as evidence that Jewish law is not as uncomfortable with the death penalty as is sometimes said to be the case.