Much of this goes back to the Samhain which far predates Christianity... As someone who was indoctrinated RC as a young child it's safe to say that most of the "Christian" holiday traditions are a hodge-podge of pagan / occult festivals, rituals, and rites...

Sooooo.... you feel you've been duped by Halloween and not Christmas and Easter? So sad! At least Halloween is morbidly fun!

Besides, the true esoteric meaning is always "veiled". How perfectly fitting for the Samhain/Halloween/All Saint's Day when the "veil" between worlds (or dimensions) is at it's thinnest.

And yes, making money has always been the foundation of most religions!!! Historically, the greatest marketers ever!