This damage assessment is as much garbage as Trump's claim of obliteration. 14 big bombs were only meant to punch holes in the most deeply fortified bunkers. Of course they weren't expected to destroy the whole program. Israel killed the top dozen physicists and engineers on the program in the first salvo. Then they had 12 days of open skies to bomb every known site in Iran. That's maybe 100 bombing sorties per day. They must have done serious damage. And it's not about the enriched uranium. You can move 400kg of enriched uranium on the bed of one pickup truck. But 18000 centrifuges, which are delicate precision instruments, can't be moved easily. They were kept at Natanz and Fordow, the crown jewels of the Iranian program, because they are the most fortified.

This. The DIA assessment is very early and doesn't have much to go on.

1) The Israelis are hunting down and killing the people with expertise. Sometimes if the right expert is removed your program can be set back for a long time, and maybe permanently. The Soviet Space program, for example, was irreversibly damaged when Sergei Korolev died in 1966. I'm not saying that Iran is as single-sourced as the Soviets were, but the Israelis are doing damage to the brain trust.

2) Uranium centrifuges are very delicate machines. Using gas centrifugal methods requires very high speeds (due to the low mass of the gas) and as such requires very delicate bearings and mechanical structures. Any shock damage - like dropping 12 30,000lb bombs onto the roof - would likely damage them in ways not easy to fix.