The fact that they were Catholic, and not Orthodox for longer after the Great Schism than they’ve been apart from her?
They may sincerely believe this, but this is the truth.
How is it, that the Roman church changed so much from the time of these two missionaries, that are recognized as saints by Catholics and held to actually be Catholics? Novelties arose in Rome but not elsewhere, clearly.
I'm beginning to think that all the odd disconnect and denial I encounter whenever this subject comes up stems from a fear of there being an invigorated, evangelical church among the Czech people, successfully proselytising Poland and beyond again.