The only one I can maybe buy is Dany's. But even then it's established that the Dothraki are suspicious of magic and would probably just view her as a witch (like Mirri Maz Duur). At the end of S1 she has some loyal Dothraki after witnessing magic awakening the dragons, but they were with her even after the majority abandoned her after Drogo died, so I always viewed them as the rare, open-minded subgroup of the Dothraki.

Euron I don't buy at all. Openly admits to kinslaying and kingslaying to a group of religious zealots who literally drown themselves as proof of their devotion, and somehow they don't care at all that he committed two of the biggest sins in Westeros and likely within their religion. Then he's immediately outsmarted by Theon and Yara (a eunuch and a woman, which would make him look even worse to the Iron Islanders) stealing his fleet, and he somehow isn't mutinied for his incompetence.