Under Papal rule, these groups of people were forced to move deeper into the wilderness and commit their scriptures to memory under secrecy, attending higher education and even entering the mission field under cover of a secular calling.
Ellen White tells us in the closing page of the chapter, "The persecutions visited for many centuries upon this God-fearing people were endured by them with a patience and constancy that honored their Redeemer. Notwithstanding the crusades against them, and the inhuman butchery to which they were subjected, they continued to send out their missionaries to scatter the precious truth. They were hunted to death; yet their blood watered the seed sown, and it failed not of yielding fruit. . . . Scattered over many lands, they planted the seeds of the Reformation . . . and [it] is to be carried forward to the close of time by those who also are willing to suffer all things for 'the word of God, and for the testimony of Jesus Christ' (Rev. 1:9)" (The Great Controversy, p. 78).
To learn more about the Waldenses, read The Great Controversy by Ellen White at https://greatcontroversyproject.org/.