Why did Iran insist (and the US accede) to remove a nuclear smuggler from sanctions?

From the WSJ:

The Obama administration and European Union agreed as part of the accord last week to lift sanctions over eight years on a network of Iranian scientists, military officers and companies long suspected by the U.S. and United Nations as central players in a covert nuclear weapons program.

The U.S. also agreed to remove a German engineer from its financial blacklist by late 2023 after he was targeted by sanctions for his alleged role in a global black market in nuclear weapons technology run by the father of Pakistan’s nuclear program, Abdul Qadeer Khan.

Obama administration officials said the U.S. was required under the Vienna agreement and U.N. resolutions to lift sanctions on Iranian individuals and entities for their role Tehran’s nuclear program.

Lawmakers and nuclear experts were also puzzled by the Obama administration’s decision to remove Gerhard Wisser from its sanctions list by 2023. The German engineer was convicted and sentenced to 18 years in prison by a South African court in 2007 for his role in supplying centrifuge components to the A.Q. Khan black market network.

The U.S. and IAEA accuse Mr. Khan and his associates of facilitating the sale of nuclear equipment to North Korea, Iran and Libya during the 1980s and 1990s.

The senior U.S. official didn’t provide specifics about why Mr. Wisser was granted sanctions relief as part of the Iran deal. Mr. Wisser could not be located. He pleaded guilty in 2007 in South Africa to manufacturing components that could be illegally used in nuclear technology.

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A South African court sentenced a German man to 18 years in prison on Tuesday but suspended the jail term after he pleaded guilty in a case involving a global black market in atomic weapons technology. Gerhard Wisser, an engineer living in South Africa, was accused of having ties to a network run by Abdul Qadeer Khan.

Wisser was also suspected of providing nuclear weapons components to Al Qaeda!

But isn't it interesting that Iran insisted as part of the deal to lift sanctions on a non-Iranian convicted nuclear smuggler, who was involved in nuclear bombmaking?

Clearly Iran felt it could ask for nearly anything it wanted in this joke of negotiations. And clearly - they were right, since the US said, "sure, no problemo! We want a deal, and if this would derail it, then we have to give in!"

Just as they did with dozens of other concessions, big and small.