Thats like saying its weird that everytime the Cowboys lose, the military is doing drills that day. The military must hate the Cowboys. Not trying to make fun of you, just saying.
As for why the guys doing the drills couldnt go there are tons of variables as to why. The military isnt black and white as some people seem to think. The answer could be as simple as, they werent ready for that sort of actual rescue, thats why they were training. You wouldnt take a guy just starting the police academy and send him to a murder scene just because the PD is busy that night. Just an example.
"What we need are critical lovers of America - patriots who express their faith in their country by working to improve it." - Hubert H. Humphrey