Soon he discovers why she left. It had to do with a momentous, life-changing secret of hers, which had nothing whatsoever to do with him. He, on the spot, dumps her for not being honest with him. She pleads with him, and says she can explain, but he says no and leaves. She accepts this as a reasonable reaction on his part, cries, and blames herself.
They get back together a few days later after she makes a large personal gesture and then also a huge change in her life in public as a method of apologizing and asking him for a second chance. The change was something he didn't know her well enough to ask for, there were no indications he actually wanted it and there was no reason for him to want it.
Notice anything wrong with this?
Confessing your feelings is a way of life involving independently creating feelings for each other, instead of gradually creating them together, and then having one conversation that instantly changes everything (possibly for the worse -- it's risky).
Dumping her amounted to giving up on their relationship when facing their very first problem, before trying to solve it. What sort of relationship can be conditional on no unexpected and unwanted problems ever occurring? Why doesn't he want to attempt problem solving?
One moment he's falling in love with her; the next he's ignoring her pleas and leaving her crying. What is his love worth if it's so fickle? What is he worth, if he's at any moment ready to hurt her if she does something he disapproves of too much? Why doesn't it occur to him to react by helping her improve?
They get back together without figuring out how to avoid any of their prior problems first. She doesn't seek any assurance he won't dump her again (without even trying to fix anything). He never apologizes. He doesn't seek any assurance she won't keep secrets again. She doesn't promise not to. She doesn't explain how she learned something new and has changed her mind. She simply concedes the one point he has made their relationship conditional on and he's satisfied; it's closer to extortion than persuasion.
She cries and considers that normal and doesn't seek a way of life without crying and pain, nor think seriously about how to prevent a recurrence.
When he dumps her, she considers it legitimate too. She agrees with the scheme of things where people callously dump their loved one and leave her crying without even giving her a chance to explain what happened.
Both of them blame the victim. She gets dumped and hurt, and she gets blamed for her own pain. He could have prevented it if only he wanted to, but no one blames him for choosing not to prevent her suffering.