I think it's why Taylor Swift broke up with her British boyfriend after they were together for years. Taylor is driven and ambitious. She wants to be #1. She loves the concerts, the social media, etc. And there's not a thing in the world wrong with that. But it just wasn't what her boyfriend wanted, he was more private. It's hard to be private when you're dating Taylor Swift, lol. At least her NFL boyfriend seems perfectly happy in the spotlight, and has been since before he met her.
And so often, I see this become the answer to "the one that got away" - a reminder that there was a reason the relationship never worked before. Ben and Jen clearly love each other and probably always have on some level, but there was a reason the relationship failed, and they're still two different people now.
I hope Ben leaves Jen Garner be, though. LOL. She has had to put up with so much from him even after divorcing him. They can co-parent, but maybe stop tagging her in to drive him to rehab.