Iran probably wasn't following the JCPOA, denied inspectors access to certain sites, and you'd also have to say you 100% trust American intelligence to verify that Iran isn't building a nuclear weapon in secret and if you want to do that I've got a war to sell you in Iraq.
Separately that doesn't resolve the other issues, funding militant groups, &c.
Separately that doesn't resolve the other issues, funding militant groups, &c.