I've overlooked an important aspect for my new super-cool faith...
Nothing more says, "I'm so hardcore about my particular brand of Sky Fairy (or Sky Fairies as may be the case) that I am wearing this outrageous thing on my head."
See? Those serpents are getting the Hell out of Ireland because of St. Patrick's badass hat. Look! It has a halo around it signifying it's badassery! How else could St. Patrick sell the Irish on anything as ridiculous as the Trinity?
It was THE HAT!
It's cross cultural too. When Mayan and Aztec priests were doing all those human sacrifices they needed a little something something to keep their hair in check.