Most of the elite do in-network socialising and marriage is a good way to increase or improve your social network, considering Jews are probably the most powerful elite group then its no surprise we see a lot of Jews marry gentile elites (either the Jew marries to increase their own influence or the gentile gets married to garner goodwill with some Jewish oligarch). I mean historically, marriage has largely been a "diplomatic" thing in many ways even among low class families in many cultures because arranging marriages was a sort of "deal" to establish social partnerships between families (you still see this in MidEast and other parts of Asia).