Perhaps you should say "reformers". It may or may not have been mistaken---that is yet to be seen--. There have been many popes and who knows how many more there will be. It is easy to see why they thought that at the time given what was going on with the popes. And it was based on something and not simply a Dispensational interpretation of Scripture. The pope was, and still is, standing within the church, claiming to be The Church, which Scripture tells us is the temple of God as it is Christ's church, and his people also called the temple in Scripture as the Spirit indwells them, standing there {the pope} declaring himself to be the only interpreter of Scripture and the church's priests the dispensers of saving grace. (God iow).