Neither of those reasons are necessarily required to believe in a conspiracy theory.
Plenty of objectively smart people succumb to conspiracy theories. I am almost certain you have unfounded beliefs that when scrutinised make no logical sense.
Often it is just that a person has been disenfranchised and in a vulnerable position where seizing upon a conspiracy theory gives them a sense of control, community and power.
It was a marketing campaign from De Beers. Where else would it have come from.