Catholicism flowed from Judaism. All the first Catholics were Jews until the Apostles Baptized Gentiles (Acts 10)<quoted text>
Many Protestants were taught that by their Protestant theologians.
It was and is the divide and conquer method. Protestant theologians taught that if people followed them, they would learn what real holiness meant, and that would be sure to align the followers to the will of "God."
The ex-Jew Catholics spewed, and many still spew the same type of nonsense about the Jews not having the WHOLE story. Jews were supposed to become devout Catholics in order to be saved ... which is very humorous considering that the supposed savior was and IS a faithful Jew.
No one can understand the Catholic faith unless they are familiar with the Hebrew Books of the OT. That's the big difference in how the Protesters do not understand the fullness of Christianity. They essentially ignore the OT. Much of what is written in the NT - especially the words of Jesus Christ can be traced to the OT.