Adam on Girls has never been a steadily good boyfriend. An interesting character, yes, and an integral part of the show, sure, but a consistently decent human? Not quite. While finding a new girlfriend before Hannah even knew they'd broken up is a particularly dramatic instance of crumminess, it's not exactly out of nowhere. Adam's quirkiness has its appeal, but it's often just a diversion from how uncaring he can be.
When we first met Adam, he was the guy who wouldn't commit to Hannah and who'd brag about how all the other women he was sleeping with never made him wear condoms. He was vile to Hannah when she admitted she had HPV. He texted her a dick pic followed by "sorry, that was for someone else." (Oy, Hannah. Run.) He wasn't up front about his sobriety. Somehow, this is love. In the season-one finale, Adam decides to move in and declares he loves Hannah, displaying no ability to consider anyone else's timelines. Then he and Hannah have a brutal argument that ends with him getting hit by a car, driving away in an ambulance screaming "fuck you," and calling Hannah "a monster." They break up.
In season two, Hannah feels guilty and responsible for Adam's accident, so she tries to take care of him as a friend — even as she admits he's "murder-y." Adam tries to win her back with creepy music videos professing his love. He steals a dog. Then he falls off the wagon and has degrading, possibly nonconsenual sex with his new girlfriend, Natalia. Hannah calls him in a moment of need and he runs — literally — to her apartment, shirtless and theoretically valiant.
Season three is their happy ending, except it's not. There are all these sweet gestures and instances of kindness, but they're punctuated by moments of selfishness. Sure, he'll rent the car and come along to get Jessa from rehab, but he's gonna slam the radio off and complain about how he can't sleep until he has an orgasm. (Please leave the room for a few minutes, Shoshanna.) Adam's adamant about how much he dislikes Hannah's friends, and he's quick to criticize Hannah's emotional reactions, as if she's in control of them. Hannah's attracted to Adam's rigid senses of what's appropriate, but that doesn't make those senses actually good. Adam does things his way, and certainty is often sexy, but Adam's brand of certainty tends to be very callous. He moves out, he distances himself — but Hannah moving to Iowa is what he considers leaving. When Hannah wanted to celebrate the news that she got into one of the most prestigious programs on Earth, all Adam can do is berate her for telling him at the wrong time, by which he means the wrong time for him.
Adam's the king of intermittent response, and Hannah is secretly drawn to this kind of unpredictability, because we see it in Jessa and Marnie as well. When Adam's there for Hannah, he is there for her hard core. He rides his motorcycle to come stay with her when her grandma's in the hospital, and he dotes on her when she's in the throes of her OCD crises. But when he's gone, he's gone hard core, too. (She could have seen it coming, too — she knows that the way he broke up with Natalia was by literally never calling her again.) That's its own kind of sin, but it's even worse to vanish or appear unpredictably. The guy who's mean to you all the time is easy to write off, but the guy who's only mean to you a little bit of the time? Maybe you can just crack his code and be the special one who really gets him.
Hannah is both attracted to and afraid of stability — adulthood, maturity — and Adam is that exactly, a kind of stability lite, for twentysomethings. Sometimes he's Mr. Reliable. Of course, an actual Mr. Reliable is Mr. Reliable all the time. I'm not saying Hannah deserves to be treated badly, but if she actually dislikes it, she hasn't tried to avoid it much. No one deserves to get stung by the scorpion, but you knew what he was when you saved him. You don't get to be surprised.
And while Hannah seems crushed, this breakup gave us a glimpse of the capacity of future Hannah, the grown-up version of what she could be. "Hannah, I want you to understand: This isn't about you," Adam tells her. "You know what, Adam? I think I really understand that part," she replies. For once, she says the right thing at the right time, and it's something that's self-validating and confident, even in the midst of an emotionally lousy scenario. Isn't that what we all want? To say the right pithy things and to believe in ourselves? It's a weird little moment of hope that's of course followed up by awkward fumbling. She might be showing increasing signs of maturity, but she's still Hannah.