's not clear why, yet, but the B-2 is a difficult aircraft to crash due to pilot error: the onboard fly-by-wire systems have limiters that prevent "overflying" the aircraft, and the B-2's limiters, unlike those of more high-performance planes like the B-1B or fighters, are very nearly ironclad. You can't push them, they don't work that way, because due to its flying wing shape a B-2 without positive control is something no sane pilot contemplates. You don't do spin or stall recovery in this plane, you eject.
On the other hand, the B-2 is an extremely difficult aircraft to fly without the extensive computer support. A total electrical shutdown is a major problem, again, due to the flying wing shape. The computers make a multitude of minor adjustments every minute to keep it stable and flying well, and with them, the aircraft is very stable, easy to fly, and actually quite agile for its size and speed. Without the computers it becomes inherently unstable and extremely demanding.
Because it crashed on takeoff, the possiblity exists of FOD being at fault, and I don't really know how well the B-2 responds to a lost engine situation, but it does have several of them, and it is rated to be able to fly with only half.
