The motivating question behind Jared Diamond's Guns, Germs, and Steel is why Europeans came and conquered America, Africa, etc., rather than the other way around. And one can make a similar observation with respect to religion: Why did Christianity flourish and become the largest faith in the world, while Judaism remains comparatively tiny?
Today, I think I hit upon the answer. And it relies on "once-a-year" faith adherents.
Suppose you're a once-a-year Christian. What is that one day of the year like? It's pretty good! Presents, and bright lights, and beautiful conifers, and carols that remind you of the happy innocence of childhood. It's a great celebration had by all.
And if you're Jewish? Well, your one day a year involves fasting the entire time while thinking about how bad a person you are. It also involves no songs that remind you of your childhood, because the High Holidays are when we give Cantors a free pass to simply make up tunes that are never remotely familiar but are always 64x longer than their every day equivalents.
What I'm saying is, have an easy fast and a contemplative Kol Nidre and Yom Kippur.