Complex sentence: But Dagobert does not know that the pope, while he is still traveling he is replaced in a conspiracy by a perfect double, who is a crude and rude man, even more stupid than Dagobert.
Split into simpler sentences: But Dagobert does not know that the pope, while he is still traveling, was replaced in a conspiracy by a perfect double. The replacement is a crude and rude man, even more stupid than Dagobert.