There must be some motive here that I can't understand. For one I can easily think of reasons why the US wouldn't want to make public the things that they know, if not for any other reason than to risk revealing how they know what they know. Other than that sometimes it's better to not let the "adversary" (for lack of a better term) know that you know the cards they are holding.
On the other hand I can think of reasons why you wouldn't want to keep making these kinds of announcements, like freaking out people in Ukraine. Wouldn't it be better to just tell the Ukrainian government what you know and let them decide how to handle the public relations in the matter?
It just seems very surreal, if you watch the mainstream news or listen to the President or other officials making statements they claim to know these very specific details but I can't figure out why we are hearing it from the US and no other source, or why we are hearing it from the US at all.
This seems like a multi-faceted question but really it comes down to why is the US specifically pumping out all these statements and claims about Russia/Ukraine in the first place? What could the possible motive be for the US?