Trump was able to bring Iran's nuclear program to a trickle by getting rid of the one-sided treaty and imposing tough sanctions.
Is it opposite day?
Because Iran was abiding by the JCPOA (as verified by international inspections) up to the point where the US unilaterally exited the deal. About the worst thing that the Trump administration could level at Iran was that it had not fully revealed past efforts (in the 1990 and up to about 2003) to develop an indigenous nuclear weapon capability. The month before the Trump administration pulled out of the deal, the US State Department confirmed it was abiding by it.
Despite the Trump administration's claims, Iran was meeting its commitments to the deal and was not enriching uranium beyond what was allowed under the agreement. It had cut it's centrifuge capabilities by two thirds, completely reduced its medium enriched uranium stockpile and cut its low enriched stockpile by 97%.
Fast forward to 2023 and Iran has pretty much resumed Uranium enriching activities, to the point where it now in violation of the nuclear non-proliferation treaty. Iran has gone from possessing less than 300 kg of low-enriched uranium (~3.7%) to producing more than 9kg per month of 60% enriched U235 and has been found to be producing 84% enriched uranium (90% is needed for weapons-grade material).
Iran need money to support terrorism and to create a nuclear bomb.
Which it gets anyway, thanks to trade outside of the US and Europe. Basically because the Trump administration ended nearly decade years of detente and five years of careful international diplomacy, because (and I'm paraphrasing here) Trump got bad vibes from the deal.
The treaty turned out to be a nightmare, it allowed billions to go to Iran, did not allow inspection of a number of military sites, and the sunset provisions were killers.
The sunset provision were for 10 and 15 years from the signing of the agreement, and weren't killers. In fact and were open to renegotiation under article V of the agreement.
The 10 year provisions allowed Iran to build it's centrifuge capacity back to ~20% of what it was before the agreement from 2025 onwards. From 2030, Iran would have been allowed to develop it's centrifuge capacity but was limited to enrichment levels of under 5% (under it's agreements
Right now, Iran is operating almost 150% MORE uranium centrifuge capacity than it was in 2015. It has, by some estimates, enough capacity to produce uranium for five to six weapons every year.
Same story with enriched uranium. Iran would have been held to a limit of ~200 kg until 2025 and 300 kg to 2030. Instead, Iran now has a enriched uranium stockpile of 4500kg.
One watchdog agency reports Iran has "reached the point at which, within three weeks, Iran might be able to enrich enough uranium for five fission weapons" although weaponisation "could take anywhere from several months to a year or more, although the timeframe is uncertain".
Trump withdrawing from the JCPOA pushed Iran
RAPIDLY back down the nuclear path. Even if the agreement had fallen apart in 2030 and the sunset provisions hadn't been renegotiated, Iran would be
at least a decade behind where it is now in efforts to acquire nuclear weapons. Iran is further along towards nuclear weapons now than it was in 2015.