And you believe that Iran will actually comply to IAEA rules.
I talked about this in my post a little, but I'll make it explicit.
The Iran deal does not rely on trust. In general, international diplomacy is not about trust, but about consequences.
If Iran allows IAEA inspections and tries to carry on a nuclear program of any reasonable capability, we'll know immediately, and the sanctions will come back.
If Iran stops allowing IAEA inspections or attempts to limit or control them in any way, we'll know immediately, and the sanctions will come back.
If Iran allows IAEA inspections and tries to carry on a very small, very secret nuclear program, it'll seriously increase the amount of time they need to create a bomb (which, again, is the goal), and we'll probably find out eventually, and the sanctions will come back.
No trust is required for any of these steps. This is all verification.
In all three cases, having created and kept to our part of the deal, we'll isolate Iran and make it much easier for us to get the cooperation of international allies including Russia, China, and possibly other Islamic states. By contrast, if we allow this deal to collapse or deliberately undermine it, we'll be isolated, and we'll lose not just Russia and China but very likely western Europe as well.
Once again: the only way for us to stop Iran from creating a nuclear weapon that won't rely on constant inspections and verification is for us to permanently occupy them. Even if we were to occupy them, forcibly dismantle their nuclear program and institute inspection protocols of our own, as soon as our troops left Iran they'd repudiate the inspections and kick our people out and we'd have to go right back in.
We can't, and won't, permanently occupy Iran. We have no capability to permanently occupy a country in today's military era, we have no will for a prolonged war and occupation, and there's no way the international community would allow us to do it.
So there's no way for us to stop Iran from getting a nuke. The best we can do is set up a system where they promise not to build one and we verify that they don't.