Are the schools of thought, the People of the Sunnah, and the people of innovation and desires among those who divided their religion and thereby caused the Ummah to become divided?

The adherents of the four jurisprudential schools (madhahib) are committed to the Qur'an and Sunnah, and they agree on the fundamentals of religion and its general principles. Their differences in the subsidiary matters (furu') have logical reasons, such as not being aware of a text, or a difference in understanding. They are Ahl al-Sunnah wal-Jama'ah (the People of the Sunnah and the Community). As for the other sects that differ on the fundamentals of religion and its general principles, these are the ones that divided the religion and caused disunity within the Ummah.