This problem and laws came from the Babylonian exile. These laws were created from the sect called the Pharisees that YAHSHUA had to constantly contend with. After the destruction of the Temple, in later centuries many of the Pharisees return little by little. The Sadducees, the priests (YAHSHUA had to deal with as well, but not as much as the lawyers called the Pharisees.) were no longer needed and the Levites died out! That is why people today should not believe in those who called themselves Kohanim. They claimed their bloodline is from Aaron, which is not true historically and Biblically.
When the Romans destroyed the Temple, it was the Hebrew nobles, priest, and Pharisees that were taken and placed into slavery. These are the ones that incited the people to revolt. Many Hebrews where they were disperse were forced to become Catholic or Muslim, very few kept their faith. The Pharisees was a sect and not related by blood and some escaped to Egypt before the war. Hadrian became emperor many of them slowly returned to Israel and Jerusalem and begin to formulate. They formed a new Rabbinical religion called Judaic that spread with many of the old teaching and doctrines that had already changed in Babylon before the time of the Maccabees. The problem was they had to deal with the Sadducees now the priest bloodline was gone and they could openly claim the Talmud and their practices. Those who were sent to Europe became associated with the German people around the Rhine River.
Again, they became rich merchants but they remain cut off from the German people. More and more over the centuries, they would marry among themselves first, and later their youth would marry the Germans. Like the Catholic, the female German would adopt the belief and raise the children and now they were called Jews. These communes begin to spread all over Europe.
It was totally different in Russia ever since the Babylonian, Greek, and Persian dominance many Hebrews did not return to Israel. The Hebrews were merchants and formed communes in Turkey and again married and intermingle with caucasian people of various tribes spreading to Crimea, Georgia and other countries eventually they migrated into Russia as well. This is when the Kingdom of Khazar joined into the belief. Understand that the belief of the Pharisees came out of the Babylonian captivity and this belief spread with the Pharisees everywhere. Only in Israel did it have difficulties because many of the priestly tribe returned to Israel. Once, the Levitical tribe disappeared and the other tribes intermarried and like the Bible stated that Japheth would dwell in the tents of Shem. This became a reality, also the curse upon the Hebrew happen as well. When Rome came on the scene the Hebrews were spread all over the world and they mixed Hellenization of the Greek in with their belief system. The Sadducees oppose Greece that is why the Maccabees wars became very important. They were the priest, but they also did not practice all the truth themselves, however they clash with the Pharisees. They only united together to killed YAHSHUA who was a thorn in both of their sides. Eventually, as Noah prophesied, the Ashkenazi, Gomer son became the dominant one and the Hebrews bloodline because of the curse became lost!
They refused to walk in the Statutes and Commandments of YAHWEH and to present the truth to the children of Japheth and Shem seed became lost forever! Gen 9:27; Deut 28:15-68
Blessings!