It's only after babylon that the world got thrown into rebellion
& utter sin. So i was saying even in Noah's time, he was
observing marriage to a single partner. But the rest of the world
corrupted themselves sexually even with angels & homosexuality.
So there is a parallel to now. Sexual immorality is rampant with
multiple partners, so what do you think God will do? That's why
humans got further corrupted & the marriage institution was
destroyed temporarily until Christ came. We are still in Babylon
but we will come out of it soon. This world's systems will perish
& only those who trust in Christ's saving blood alone will be
saved bcos who can stand in the final day?