History speaks for itself.
Before the Reformation, there were two major schisms that persisted: Oriental Orthodox and Orthodox. All others were supprress and fixed. In the West there was the Western Schism in the middle ages. There were also a host of heretical groups throughout the ages: various Gnostic groups, donatists, etc. After and since the Reformation, we now have Lutherans, Baptists, Anglicans, Presbyterians, Quakers, Methodists, Seventh Day Adventists, "Non Denominational", Wesleyans, United Church of Christ, Pentecostal, Word of Faith, and more. There are also now very unorthodox groups with no basis in history like the Mormons, Jehovah's Witnessses, Clans Christadelphians.
All of the groups listed here have contradicting beliefs on one or more major issues. All of them are "read[ing] Scripture ... and gain understanding through the Holy Spirit." The Reformation was about political change as much as it was about theological change. Religion in general did not have the power it once did. It made schisming over disagreement OK and sparked the events that would remove the power of the Churches to deal with such schisms (that mostly came around the Enlightenment).