It's not, the Oedipal complex is a correlation. The "marrying one's parent" phenomenon most certainly has a psychological causality somewhere, but it's certainly not due to a generally applicable Oedipal complex.

A concrete example, the only relatively comparable thing I've had to deal with was tending to select romantic partners based on how familiar my dynamics with them were to me. Having lived in an unhealthy familial environment and with relatively few childhood friends, the only familiar I had was belligerent and punitive. Otherwise, none of my parents, or even from my extended family, are my type. I'm saying this in a literal sense. And this is against a constant, solid background of "like...no, they're family."