It’s based on the fact that their reported returns are so absurdly far on the long-tail of being an outlier as to suggest there is more to it than “they’re just good.” I don’t know for sure—but it’s close enough that I’d bet a lot of my own 7-figure net worth on it.
Also, I only know of WSB from articles I’ve read: your implication is rude and uncharitable at best.