Defense branch men get done like this over and over again. Why? When you're young, and your life is at risk because of your job, you're more likely to commit to the first woman that agrees to go out with you.
This man reacted the way I'd expect a teenager to. His brain and emotions were not ready for the grown man responsibilities of fatherhood, marriage, and home ownership. Any man who gets married before 30 is taking a huge risk with women who are in their 20s and are on social media and familiar with dating apps. Those kind of women can't have stable relationships. An ex boyfriend or former friends with benefits stay on her social media pages liking her pics and commenting. While dude is off on duty, she looks at herself in the mirror post-pregnanct stretch marks and all. She feels bad about how she looks, can't easily access you for compliments and even if she did, you're her husband. Of course you'll tell her whatever she wants to hear. It's like her mom telling her she's cool, it doesn't mean anything to her. So then she gets curious and thinks about her days of being single in college before she met her man.
She opens up an app just to see if she can still attract male attention. She can. She feels a rush of validation, then posts a new pic on social media. The men she used to mess with comment and DM her. Eventually she reaches her breaking point and messages one of them back.
You know the rest.