Just finished watching 'Last Days in Vietnam: American Experience" (first shown in 2014?) on PBS Maine.
Great that so many got out but watching those 410 left sitting in the Embassy Compound still hoping to be flown out..... heart wrenching.

To me, it seemed that the slowness of the American Ambassador to fully grasp the situation and refusal of Ford to do something to at least slow down the advance of the northern army contributed to the situation.
On the other hand, I suppose at least half of South Vietnam would have left if possible.