A lot of people who appear to move on quickly have been in relationships which have been dead for years and years. Sometimes it just takes a lot of introspection to realise your relationship has petered out and leave.
Men tend to ruminate about things for an eternity before they make a final decision, hence why they get a reputation for "not talking". This gives the impression they've upped and left on a whim, then moved on within a few weeks. It isn't always the case. They've often spent years ruminating about a relationship without giving much outwardly sign of it, they finally decide or realise the relationship is over, they leave, and they can move on quickly afterwards because they did their mourning for the dead/dying relationship while they were still in it.
I'm not a man, but I'm not at all emotional, or spiritual, and very rarely feel any need to "talk" about such things. I've always felt that if a relationship is really that problematic that it needs constant discussion, then it isn't a worthwhile relationship to begin with. I was with someone for 20'odd years, perfectly happy for the most of it, but it still took me 5 years or so of not feeling right to realise the relationship was irretrievable and leave. I felt crap for one solitary week, met someone about a month later, and have been perfectly happy since. No mourning period required, I didn't "move on quickly", I just did the miserable, moping, "find out about myself" bit when I was still in the 20'odd year relationship, so I had no purpose for a fallow period before I could "move on".
It's the same for a lot of people who appear not to care. They've just grieved their relationship while they were still in it.