Why do you think congress doesn’t have this information? Cohen testified to these facts.
I suspect they don't have this specific information. Indeed, I'm not sure if it could be called information at this stage.
Of course, this conversation is much less fun now that Mueller made my point for me - being smug and coy about it just doesn't work anymore. My point was that if these sources had credible information, they would have disclosed it somewhere that matters. Congress seems an obvious choice, but a reputable journalistic outlet (as opposed to a pop blog) would also be a good start.
To be clear, I'm not suggesting it must be false. But clearly they didn't have enough to go with to show that it's true. That's why they went to Buzzfeed and made a quick buck.
I guess the main problem here is that people seem to mistake Buzzfeed for a news outlet. Again and again and again. The public didn't learn from the Trump "dossier" and they probably won't learn now, either.