They don’t.
They want to preserve their economic ties to Iran, which is why they lobbied Washington to preserve the deal.
But they’re resigned to the US abrogating it, which means the deal is dead and Iran is as likely to retaliate against Europe as against the US.
For the Europeans all they worked for with Obama and Kerry appears to be going down the drain. They’re not happy.
Well Merkel did say "Europe must take ‘our fate’ into own hands"...after the G7 Summit and NaTO gathering when Trump made his presence known that he wasn't one of Merkel's pet followers....she's had her pants in a knot ever since.
The agreement demands that the signatories defend and fight on the side of Iran in the event of a war or conflict with Iran...That pits Europe and the U.S. against Israel...I'll bet Obama was grinning from ear to ear when he signed it...
The signatories to the deal include Russia, China, France, UK, the EU, Iran, and the US. Why should the exit of the US end the deal? We left TPP and the Paris Climate Accord and they survived.
It is up to Iran to decide if it still honors the agreement. If Iran leaves, then it demonstrates that Iran was always bent on getting nuclear weapons. There could very well be an ongoing clandestine program despite the verification inspections. Iran lied at the very onset of the deal.
It is ironic that Russia is part of this deal. The Dems are calling for more sanctions on Russia as part of their campaign to take down Trump for collusion with the Russians. No one seems to be questioning Russia’s motives for signing the Iran deal or the part Russia played in the negotiations. Russia built the Iranian nuclear plant and has a deal to build three more.
The truth is that everyone benefited from the Iran deal except the US.