Why does God permit prelates to promote novelties? Sedevacantists fail God's test.

https://www.newadvent.org/fathers/3506.htm

“But some one will ask, How is it then, that certain excellent persons, and of position in the Church, are often permitted by God to preach novel doctrines to Catholics?… Blessed Moses… writes thus in Deuteronomy… ‘For the Lord, your God, trieth you, to know whether you love Him with all your heart and with all your soul.'”

Sedevacantist fail the test; they run oft out of the Catholic Church Jesus Christ established and remains  the Head of.

Those who pass the test are the faithful who stay in the Church and maintain Tradition.