I imagine that it's perpetuated by the myth that people who make a shitton of money "legitimately" (ie getting insanely lucky by inheritance, investing in a moonshot, or both) are somehow magically blessed with the wisdom to handle money in a way that commoners are not. Plus a dash of cope for all the people who will never touch that amount of money. Assurance that even those who gain a lot will be no better off (or worse off) than them.

I also think the myth of “winners lose everything eventually” is a specific instance of general hate against gambling…

AKA “the house always wins” philosophy