was allow Iran to build up there nuclear program legally
You don't "build up" a nuclear program by freezing enrichment at a non-nuclear level of 3.8%. Exporting 98% of the low enriched material already present. With that restriction remaining in place till 2030. Reducing the centrifuges by 2/3 till 2025.
Along comes Trumpski, and now Iran is threatening to reconstitute their nuke program, to where it was with no limits.
Sanctions will not cause every drop of Iranian oil to be cut off. The Chinese are willing oil buyers, and the Russians will be glad to help launder the oil. Note the evil Obama (gonna take your guns away, and put your kids in Muslim youth groups) had total buy in from China, and Russia. Trumpski has no buy in for starting over.
Let's assume the Iranians came to Trumpski with turban in paw willing to give up its nuke program. How has that worked so far with North Korea? Does Trumpski and the Ayatollah have to fall in love with each other, like Trumpski did with Kimmy? Has Kimmy invited in US inspectors? Free to go, and inspect anywhere they please? Well, did the "fire and fury" do the trick? Sure seems the love letters, and box of chocolates hasn't. So how would inspections work with Iran. To ensure all unknown nuke production sites were disclosed? While Trumpski waits for Iran to capitulate which they won't, how is the US going to prevent Iran from enriching Uranium up to bomb grade?
Now that evil Obama did a simple calculation. Outside of bombing, and invading Iran there is no way to prevent Iran going nuclear against their will. So why not instead delay till 2030. Get their agreement to do so, with China and Russia supporting that timeline. Then the US has till 2030 to decide what to do next. If the US doesn't go broke due to the idiotic WH economic policies (if one wants to call them that), then maybe by then we'll have an effective ABM. If that fails one can always bring Bolton back from the grave, and start a non-trivial war with Iran.
No doubt Trumpski will have the answers to all Iranian problems. And if he doesn't, he can always ask Putin for advise.
You are full of shit. During the deal everything was verifiable. Plus the deal actually lasted 25 years for production on uranium. What do we have now - nothing which is why American Conservatives want war.