Sudden break up

So recently my boyfriend (M 27) broke up with me (F 23) suddenly after 6 months. There were no warning signs at all. Just woke up one day and decided that he wants to be single most likely forever, that it has nothing at all to do with me, he just doesn’t want to be with anyone because he’s ‘happier’ that way.

I’m the first serious relationship he’s had since his ex (over a year ago) who completely messed him up. It was very toxic and I’ve heard this not only from him but also his parents and his mate.
When we got together he had told me that he swore he would be single forever but he met me and that changed everything for him. His parents told me that when he met me they saw something change in him and they’ve never seen him more happier.

I’m really struggling to comprehend how someone can be so in love and then one day do a 180 and decide that they actually don’t want a relationship ever.
Everyone is incredibly shocked by it considering how much he was telling people he was in love with me.
I guess what I’m trying to ask is whether I’m wrong for thinking that this isn’t about him wanting to be single forever, but perhaps a commitment issue and that he’s scared to be vulnerable again because of how quickly we fell in love and how broken he was the last time he opened his heart up to someone?
Has anyone been in a similar situation whether you’ve been on the receiving end of it like me or maybe you were the person who ended it because you felt the same as my ex? What was the outcome and did they ever come back and/or decide that they actually do want a relationship?