According to critics of the Iran deal, Obama got played. If he had just waited, they argue, painful economic sanctions would have forced the Iranians to cave completely. And when that happened, the United States could have taken down Iran's nuclear program entirely, instead of just limiting it.
This narrative sounds compelling. It's also a total fantasy. The way sanctions actually worked means that the longer the US waited to make a deal, the worse it would have been.
Miles Kahler, a distinguished professor at American University, put this point really well in a piece for Brookings. Kahler's basic point is that the deal isn't just an agreement between America and Iran — it's a deal between America, Iran, and America's international partners. People who say there was a better deal don't really understand what countries like Russia and China wanted out of the negotiations:
Each of [America's] negotiating partners—three European allies, Russia, and China—paid a higher economic price for these economic sanctions in trade and investment foregone than the United States, whose companies have had (and will continue to have) limited economic exchange with Iran since the revolution, prevented by layers of unilateral sanctions imposed by successive U.S. administrations. Without the support of its negotiating partners for extending or deepening sanctions, their effectiveness would be immediately undermined. Given the greater opportunity cost of sanctions for them—particularly for Russia and China—it is difficult to imagine that they would follow any U.S. pursuit of a tougher bargain. Thus, the deal that is on the table represents not only a bargain between the P5+1 and Iran, but also a bargain among the P5+1 partners themselves.
In other words, the sanctions that led to this deal depended on the participation of those other countries. But because they previously traded a lot with Iran, they were also suffering a lot from the sanctions. America didn't have strong trade ties with Iran in the first place, so it felt much less economic pain. But Germany and China didn't want to give up the money they could make from Iran forever. If Obama walked away from this deal, these countries would likely have given up on sanctions altogether — and the prospect of a "better deal" would have vanished.
This is a very basic, fundamental point, but no deal critic has been able to answer it in a remotely plausible fashion. That's probably because the supposed "better deal" is 100 percent fictional. It was never a real option — just a myth made up to obscure the truth that this deal was the best one available.