Why do I keep seeing posts of married straight men saying their egg cracked?

Their wives don’t support them in most cases and they feel betrayed. Their wives end up hating all trans women including us straight trans women. What does it mean egg cracked? Most of us knew we were a girl since we were a kid. We may transition then or later but we knew. Egg cracked sounds like an epiphany like they never knew before. If they did know, why get married and make someone else’s life miserable?