It started in high school. There would be an occasional guy who would brag all the time about "this chick I fucked." In every case, he was lying. He was bragging, and in his case, there was nothing to back it up. What they said reminded me of what Sam Spade (Humphrey Bogart) told the Wilmer the gunsel in The Maltese Falcon: "The gaudier the punk the cheaper the patter."
I see the same thing in the Manosphere. These PUAs who have entire sites about "this chick I banged" and "that chick I banged" and "my first Japanese chick I banged" and "my first Brazilian chick I banged" are lying. They are the equivalent of those high school boys I knew. Braggarts, blowhards and liars, who tried to raise their self-respect - and gain the respect of others - through lies instead of actually doing something.
In high school when I or someone else called these guys on their lies they got defensive. If we mocked them and ridiculed them they stopped with the lies, since they were no longer trying to validate their self-respect with us. It's not like they had much self-respect in the first place.
Because these guys are liars and have little self-esteem, they will sell out in an instant.
I became fairly popular in college (I did okay in high school). I was popular enough that I was the object of a lot of vicious envy from guys and girls. I never bragged about the girls I got. In fact, somebody who is good at something never brags about it. He doesn't have to. Everyone else can see what he is.
I will say one thing, and I am reluctant to say it: my count with women is quite high. And out of all of them, only three meant anything to me. The rest meant nothing to me emotionally. That is why those who devote their lives to physical pleasure become degraded. I have seen this with "professional' PUAs once than once - and they never bragged either, and in fact ultimately became regretful about their ruined lives.
Everyone seeks self-respect. That's how you gain well-being, how you flourish. You can gain it by actually doing something useful, or you can just lie.
After all, remember that old saying: "Those who can, do. Those who can't, teach."
And what are the liars of the Manosphere trying to do? Teach, of course.