Ex man

Back in May, I got to know this guy over ig. We did go to the same college so we didn't know eachother that well. He didn't know how much I liked him from the start of college (September 2022). I followed him on ig, he followed back etc and then I tried to speak to him first. He seemed like a nice person over text, he wasn't dry at all either. After 3 days of getting to know eachother over ig, we stayed up until 4AM just talking to eachother about our childhood and traumas. It was nice. Days went on and we got closer and closer until I confessed to him and told him I liked him. He was hesitant at first because he said he can't do long distance and if we have to move universities then we can't be together. But then afterwards, he reconsidered and we decided to date. He wasn't toxic at all, he was always so nice and funny but he was also VERY insecure and was the type to victimise too. He knew how gullible I was abs made it seem as if the whole world was against him. We dated for 3 months and it was going so well, we never fought once. Come September (2023) and he suggests we break up, I was confused because I thought it was going well but then I said "okay let's break up" because I'm not going to force someone to stay when they want to leave. His main reason was "you deserve better" and "iF we have to move away for university, i won't be able to handle it" which was fair but..tell me why 2 weeks later he's with another girl? And they're dating and everything?