9G,
Your Monday-morning quarterbacking is coming from the standpoint of somebody without experience, but since you're self-effacing and humble, here's my take, minus any speculation.
Transport category aircraft, both civil and military have specific performance guarantees in regard to accelerate-go with an engine failure occurring after V1. Military FE's are extraordinarily well-trained compared to their civilian counterparts. It's unlikely that you'll see anything involving an error on the takeoff data card or preflight performance planning. The military briefs even routine flights to a degree you would not believe. Like any airline guys, this crew would have been simulator trained and proficient on a variety of abnormals including ones similar to what may have happened.
Unfortunately, there are simply too many variables and possibilities for anybody here to answer what happened. Even the mishap crew at this point is probably not aware of everything that occurred on the jet. Although aircraft performance is guaranteed, the margins are small, and there are abnormals that will kill even a competent crew that did everything right.
Here's an example. Some former colleagues of mine were departing BIKF (Keflavik Iceland) in a Lear 35. Full of gas and people. Legal. They experienced an explosive MLG tire failure 2-3 knots below the V1 speed for their takeoff. The PIC elected to abort. They did a 360 degree groundloop during rollout, skidding to a stop less than 100' from the end of a 10K runway. (With a much lower accel-stop distance for that particular takeoff.)
"Stuff" happens. (In other words there's sometimes a huge difference between what we real pilot get out of the jet versus what the test pilot got while collecting data points in the carefully controlled flight test environment.)
Does this help at all, Sir?
(I've never flown anything much bigger than 50K pounds, but the heavy guys on here will tell you the one thing they never want to see outside the simulator is a catastrophic failure involving engines or tires on a heavy jet close to the runway at MATOGW.)
Any of you FRED guys or gals want to pipe in here and help this guy understand why there's no such thing as a routine (read that easy to handle) engine failure during takeoff on the C-5?