As pointed out, there are three sources of attitude information, the left and right displays, plus the standby, when two out of three should agree, with the standby often referred to as the "tie-breaker," since it's assumed that it should agree with the left or the right display, whichever one is correct.
From what we've been told, it reads as if the PF took the aircraft and tied it into a knot chasing an unreliable attitude display. From that point it was probably very difficult to figure out just what the airplane really was doing since it would have been at some extremes of pitch and bank, plus at negative G at times, and all on a dark night with little or no outside references available. Then to look at three displays and to pick the two that were correct would have been pretty difficult.
Is that 90 seconds from start to impact? That would imply a vertical speed of about 20 thousand feet per minute, or 300 knots.