I think this would have already been published if there was genuine substance to the story. Why drag it out and offer to “sell rights to the story some day”.
Clearly the person is on a Wikipedia “hate” website and is making some pretty serious claims, by this logic - isn’t withholding the story also continuing to harm the people he’s trying to protect?
I think the two words you were looking for were "financial gain". Because let's be honest, the person clearly wants to be paid for this story as he himself has said so, and I am not saying he shouldn't get paid for his work.
But if you have to choose between never publishing your story and publishing it for free, I'm pretty sure the latter is a clear choice. And at the level he is talking about it, it would spread like absolute wildfire (if what he claims is true and he has irrefutable evidence) that Wikipedia could never stop even if it tried.
I'm willing to acknowledge the possibility that this person has exposed himself to Wikipedia directly and if the story was to break he would be liable, but that isn't made clear so I think I'm sticking to my point of view at least for now.
It turns out that Daily Beast had killed the story about the dark side of Wikipedia, which is chiefly about how Wikipedia treated women badly with harassment and doxxing, particularly by powertripping admins.
Clearly the person is on a Wikipedia “hate” website and is making some pretty serious claims, by this logic - isn’t withholding the story also continuing to harm the people he’s trying to protect?