It was not last summer's rollercoaster, when Iran and six world powers clinched a deal to end the decade-long impasse over Tehran's nuclear programme. But the announcement, last weekend, that Iran had fulfilled its obligations under the deal, paving the way for the lifting of international sanctions, was not without its drama.

Diplomats announced the release of five US citizens held hostage by Tehran, in exchange for a US presidential pardon for seven convicted felons, held in US prisons for aiding Iran evade sanctions. The breakthrough coincided with the deal's implementation and boosted the Obama administration's claim that diplomacy with Iran had worked.

Despite Iran's seizure of 10 American sailors in the Gulf a few days earlier, it appears that the deal's happy ending has come to fruition.

The agreement's cheerleaders claim that diplomacy has strengthened the hand of the more moderate factions inside Iran; established a direct channel between the US and Iran which facilitated the solving of crises unrelated to the nuclear standoff; and has thus made it possible for other regional challenges to be more constructively and effectively addressed.

It remains to be seen whether the nuclear deal will stand the test of time. Critics have pointed out many of its flaws, not least of which is the fact that the verification and inspection regime fails to fully shed light on Iran's past procurement activities and is insufficiently tasked to investigate and detect clandestine activities at non-declared facilities. The early lifting of sanctions has also left the West with little leverage against Iran, should the regime renege on its promises or cheat.

One thing is for sure. The deal did not empower Iran's so-called moderates and demonstrated that US foreign policy itself - as opposed to a handful of its citizens - is now held hostage by the Islamic Republic.

Last Saturday, the Guardian Council, the body in charge of vetting Iran's candidates for public office, disqualified thousands from running in parliamentary elections scheduled for the end of February. It also struck out numerous candidates for the Assembly of Experts, due to be elected on the same day. The Assembly is in charge of electing the new Supreme Leader - such a poll looks increasingly possible as rumours mount about Ayatollah Ali Khamenei's deteriorating health.

Disqualifying more moderate candidates from the office means that the outcome of such an election - and the future course of the Islamic Republic - remains firmly in the hands of hardliners.

The same can be said of parliament: most reformist candidates, as well as allies of former Iranian president, Mahmoud Ahmadinejad, were barred from running. The next parliament will likely be dominated by conservatives and hardliners.

The Obama administration has long believed that the nuclear deal would be transformational - for the region, for bilateral relations with Tehran and for Iran itself. It has thus modulated its foreign policy in order to strengthen the moderates in Iran. It offered muted responses to Iran's outrageous support for Bashar el Assad in Syria; it refrained from punishing Iran for its violations of UN Security Council Resolutions on ballistic missiles tests; and it took a neutral stance when Tehran's rent-a-mob ransacked the Saudi embassy, after Riyadh executed a Shia cleric in early January. When, two weeks ago, 10 US sailors were seized by Iranian Revolutionary Guards, held at gunpoint, paraded on TV and forced to give interviews for propaganda purposes, the US insisted they had been treated properly and fairly; it denied it had issued an apology; and praised diplomacy for the quick resolution of the crisis.

We now know that all these actions by Iran were given a pass so as not to jeopardise release of the hostages.

But, shockingly, two US citizens were not included in the deal and, within 48 hours of the release of the captives, more US citizens were kidnapped in Baghdad by Iran's Shia proxy militias. It appears that Iran can indefinitely leverage hostages against the US.

Meanwhile, the US has rowed back from its declared goal of removing Assad from power; it has refrained from pushing back against Iran's support for terrorism and its nefarious backing of Damascus's brutal war against its own people; and, generally speaking, it has broadcast to its regional ally that Washington's foreign policy in the region is realigning.

This has, in turn, pushed Saudi Arabia into a corner and made Riyadh take matters into its own hands - not a recipe for stability, as the recent escalation of tensions between Iran and Riyadh shows.

Iran has extracted what it wanted from the West. The lifting of sanctions cannot be reversed easily and Iran will now seek to strengthen its economy and insulate it from outside pressures.

The flow of business into Iran will strengthen the regime and boost its legitimacy. Meanwhile, the so-called moderates, having fulfilled their role as nuclear negotiators, are now going to be shown the door by the real boss inside Iran's power structure.

Iran's bellicose attitude in the region is being bolstered by Western acquiescence. Through hostage-taking, a business Iran has mastered since the early days of the Islamic Revolution, the Islamic Republic has proven once again that it can extract concessions and score political points at a relatively low cost.

The nuclear deal will now condition regional dynamics for years to come. And judging by how little it has benefited the region and Western ability to pursue its interests wherever they clash with Iran, it is hard to praise diplomacy for the little it has accomplished.