"The Church" in the OT became corrupt over and over again, too many times to count. God led prophets to reform the Church, and for God's reasons the Church was reformed, even though it would not last for very long in many cases. Therefore, there was no need to start a breakaway group of followers. God never led them to do that. However, 500 years ago, God did lead several men to break away. Although not to the same degree, He also led either you or the Orthodox to break away 500 years before that. God had His reasons for doing it, so it was done. And if you want to say that I am comparing Calvin and Luther to the prophets or the Apostles, then just remember that all of your Fathers already have that status as a group because Tradition is equal with scripture. If numbers matter so much to be correct, then my side also has a group.
Nor was there a reason in 1520. God didn't start something new in 1520. Despite what you are trying to say, Luther and company were not the re-incarnation of Christ! Throughout the OT, despite the Jews's sinfulness, God NEVER had the prophets start a whole new religion. Christ fulfilled the Jewish religion. It's done. Luther and company are quite similar to Korah. Wanting to place themselves in power over God's appointed instruments, as bad as they might have been in leading the sheep.
I think it's been shown that Luther's theology is a massive mis-interpretation of Scriptures and cannot come from God.
Regards