Apparently it's because Bin Laden had it on his harddrive that they seized/stole during the raid that killed him. And it's not exactly like the CIA is all that fuzzed about people knowing they did some terrible shit during the cold war, since they just claim that it was a different time and that they have changed (or libs will make that argument, because they have a religious need to believe that the CIA is now the good guys after Trump yelled at them).