Given Tehran / Moscow-Tehran’s duplicity where their ambitions have been concerned, State would have known the Iranian treaty worthless before it was signed and consequently used weakness (remember Kerry’s pink tie?) to purchase time for other measures.
In that Moscow-Tehran tie together in analysis, the same policy in diplomacy has helped Moscow-Damascus destroy Syria while running down Moscow’s ready cash base. Possibly: we weren’t going to be blackmailed by the incubating of ISIS or the threat of mass migration; instead, in time-honored fashion, we have been watching the enemies of the west destroy themselves.
The Saudi deal — billions in arms — seems more complex but pursues similar ends in relation to the continued diminishment of the once Soviet Era axis that Moscow has been trying to sustain and Washington has been trying to neutralize and transform. In that the Saudis have had a long history with The English and today are today heavily invested in western success (look over Kingdom Holdings) and taking some steps to alter the deeply medieval character of the state — https://conflict-backchannels.com/2016/11/02/sixteen-women-the-kingdoms-most-powerful/ — the relationship may be more valuable than the arc of time involved in getting a medieval state that has contained itself from violently aggressing against the west — into position for updating.
That these “moves” work too slowly and across Administrations dissatisfies us, but some — well, maybe just me — who take the long view of Russian, Islamic, and post-revolution Iranian politics, the popular demand for direct-fast change promises primarily to deliver the chaos and violence of revolution and war (which may have to be met in any case given Moscow-Tehran’s commitment to feudalism, feudal political methods, and the sustaining for their populations a medieval worldview). It would seem better to maneuver both into being less ready for war on a large scale — one by allowing the leadership to run the state short on ready operating cash (Russia) and the other (Iran) by way of the modern wants of its constituents, who will find they cannot get what they want if their regime cannot contain itself.