...but it was supposed to withstand an a-bomb
Using the 50's cold war mentality, if it can withstand a Hiroshima-esk explosion, why couldn't it withstand a little water? An opening for a sump pump would have made the bunker vulnerable to nuclear attack. We know that a nuclear war did not happen, but tell that to the people of 1957. Hindsight is 20/20 boys... While I agree the current situation for the once beautiful Miss Belvedere is sad, Tulsans 50 years ago did what they felt was best for the car.
Besides, on a positive note, despite the extreme issues to the car, someone, somewhere will shell out the $ to restore that car, if just for the notoriety of being the first to drive the buried 57 Plymouth.