See, the strangeness comes from the expectation that the players involved and their institutions, are separate entities which are beholden to operating with the best interests of their respective sovereign government structures.

Were this so, ambassadors to make those phone calls would have still been around and the method used in this part of the geopolitical dance choreography.

They aren't separate entities, regardless of what the charters, laws, and mission statements say.

It is not the US and the Russian Federation's interests that this meeting was for.

An oligarch is an Oligarch first, and a member of their natal nation-state second. I hope I don't need to spend a whole lot of time going over the US side of the transnational Oligarchy.

But the head of the spy agency wouldn't be discussing the effects of an attack with a foreign nation, but he would be a good messenger to send for an interdepartmental memo going over the long term strategy and the quarterly reports, from the Operations department over to the Finance department.

Everything you said makes sense of course. What they did makes sense if you think about how orange hitler is Russian asset Kraznov - they could be trying to help Russia not make that mistake.