Kudos to those highly skilled and brave engineers, who took the gravest risks in dismantling the three detonators of a 1944, 4000lb "cookie-cutter" or "blockbuster" bomb.
The corrosion over 72 years of lying buried deeply underground would be substantial, and despite being a former military field engineer, it's not a job I'd like to be handed.
Here's U.S. military test film from 1942, showing the testing of the blockbuster bomb. They were so-called due to their ability to flatten a city block if exploded at ground level.
Here's video of an actual blockbuster in a museum, and the DH.98 Mosquito that carried it.
There's nothing sophisticated about the later 1944 models - they were just a cylinder packed with 3000lbs of Amatol and 3 detonators to ensure detonation.