I hope you're not trying to equate hostage release with a nuclear non-proliferation treaty and the end of the war on the Korean peninsula.
It happened after the Iran deal. The meeting is still on with NK and Trump. Looks like it will be fine. NK will do what China tells them to do.
Also your friends in Iran are quickly back to burning flags and chanting death to america, like they have been, before the deal. after the deal, and after the deal was dead. sarcastic: how my heart bleeds for them.
⚠️ WARNED: Flaming ~ CGI
What do you expect? They're basically "We had a deal! We followed it, we stopped everything, sold off materials and dismantled production capacities (97% of the enriched Plutonium; the 3% that's left are enough for a civilian test reactor, but not for an atomic bomb, 4 out of 5 of the generators and about 60% of the enrichers capacity (those are huge and take a very long time to dismantle both due to their size and due to radioactive contamination of the steel, hence why only 60% by now)), had scientists and UN check every month whenever they wanted (and yeah, the news about Iran not letting them check the facilities where from before the deal!) and they still cancel the deal and want to impose heavy restrictions? Fuck them traitors!"
Trump is basically achieving the contrary of what he wanted. The Iranian president, Hassan Rouhani, is a very progressive and moderate one. Part of his presidential pitch was to improve relations with the west - but with Trump unilaterally canceling the deal you can be dead sure this plan is now dead and buried (other things he did was to improve the rights of women and the individual freedom of everybody in Iran, free access to information and supports the rights of ethnic minorities in Iran. If that sounds evil to you, I don't want to know what's not evil for you). But this decision will be the perfect fuel for hardliners and extremists. Trumps decision probably crushed the dreams of all the moderates and progressive people in the country and probably has added several thousands of extremists and terrorists to some groups just in retaliation to "the untrustworthy westerners". Because for them after this, we are traitors and cheaters and holding Iran down not for good reasons, but out of spite. Hassan's successors will most probably be conservative hardliners since they can market this decision the best for them in the next elections, and all the progress he achieved in human rights will probably be lost under them. Nice job breaking it, Mr. President!
You can also be dead sure that they will not accept another agreement anytime soon. I mean, who would accept an agreement after getting cheated out of their previous one? They won't trust the west playing by the rules after this and thus surely won't play by the rules either anymore.