>DoD decided to purchase copies of the first printing because they contained information which could cause damage to national security
1) Doesn’t that finance a second printing?
2) Was it something particularly damning to the higher-ups, like proof of a conspiracy to put illegitimate ideologues into offices of power?
The second one, though, hits close to the mark.
Read the Fox News story about this Pentagon (DIA, actually) censorship and you'll have your answer. (I'm a bit surprised it hasn't been posted here, but give it time.)
They do not want the book to see light until after the elections.