4chan is the infinite racists on infinite typewriters analogy; that said, some ideas converge and crystallize and escape out of the shitposts. Greentext screenshots and images that are distributed outside of the cesspool and get mainstream appeal though e.g. Reddit.

Survivorship bias, evolutionary somethings, and curation help the shit escape 4chan's confines. I can probably word that more eloquently when my brain isn't fried.