Need a males perspective on breakups that happen and the immediate following of random new girls - why is this?

First off I just want to say that I know both men and women can do this type of stuff, but I just really want a males perspective that has been in this scenario before to provide some insight to help me move on.

My boyfriend of 10 years dumped me last month out of nowhere, removed me off everything, and I couldn’t help but to check his newly made instagram and see that he’s following girls I’ve never heard of. They’re from our city and have zero mutual friends so I know he’s met them recently and probably asked for their numbers/info.

Obviously we’re broken up and I don’t have any claim on what he does, he could get married tomorrow if he wanted to. But I just want some sort of perspective on this. Why is he doing this? He’s probably looking to rebound, hook up, meet new people, and it’s so hard for me to wrap my head around this because I’m still so hurt and the break up literally happened 30 days ago, I couldn’t even imagine moving like that.

It’s like it took him no time to be on the prowl. Did he even grieve? I feel totally discarded and thrown out like trash and find myself spiralling with these thoughts, wondering if he’s even thinking of me or feeling any hurt from the relationship.

The few guy friends I’ve spoken to said that this happens a lot with guys where they almost have a delayed emotional reaction. But none of them have been in a long term relationship like this, so I figured I’d ask you guys on here if you’ve been in a similar situation/know someone who has.

Did the hurt come months later? Was the instant rebounding and seeking out of women the first thing you did, and then felt sad months later? Any regret? Any realization that you were avoiding feeling out your emotions? All of my friends say this is a classic avoidant attachment style, is this true?

Would really love some genuine opinions on this.

For some extra context: There was no indication that this breakup was coming, promising me all week that everything was fine and promising that we were okay, he promised that he didn’t cheat on me, we had zero issues at all leading up to this. He said he wants to be single but is “very aware he could regret this” and that every girl he meets will have to live up to the standard that I set. He’s also been in therapy for 6 months, and doesn’t really have close friends. Also never had instagram until we broke up.

Obviously him wanting to be single makes sense on why he’s seeking out new women I guess, but this soon?

I appreciate any insight. I know he is free to do what he wants but this has flipped my life upside down and I’m truly shocked at his quickness to “get back out there”, while I’ve been diving deep into my emotions, self reflection, friends, journaling, and trying to heal.