While the people of Israel were divided into different sects and viewpoints in the 1st Century, all looked to the Torah as God's revelation to Israel.
Yeshua and His disciples shared that common ground with His listeners.
Sadly, religious leaders among the people twisted the Torah regarding marriage and divorce, often leading to adultery and broken families.
Yeshua corrected those false teachings in His Sermon on the Mount.
What He taught is not well understood by many even now, but when understood correctly it brings peace and freedom to all who benefit from His teaching.