He already planned on breaking up with her( when she gets a sustainable income in her job ) but when mc knew she was working at a bar, he had the perfect reason to break up with her quickly, the mc was very desperate on breaking up with her because he already found someone he actually like more.
And I think the reason why he wasn't satisfied with his first gf is because he was kind of suspicious of her, she was too dependent on him, she spends a lot of money without thinking and the MC mas getting aware that her first gf is trying to control him by just relieving his sexual desires which is actually worrying considering she likes to spend so much money.
She's actually trying to improve and try to help the MC financially cause she got the hit of reality and realized that she needs to work rather than leeching of her poor bf( still remember when mc's card literally got declined in a convenience store lmao )