Especulation.
1) Part of the ground sensing ,change to flight condition.( A circuit breaker open or some wrong in relays or circuit)
2) Pilots, during first takeoff intention, notes the RAT increase and EPR reduction ( Rat probe was heated)
3) The mecanic not detected the condition and choice disconect the heater feeder wire ( the plane stay in flt condition)
4) In this condition the Take off configuration warning is inoperative.
5) The roll inestability is típical a stall condition because the wings d´not enter in this condition simultaneously.
6) when there are some problem ,the pilots atention is focused in this and rest is out of the loop.
PD : The flight recorder start in ground whith either fuel lever is open and parking brake is release. In flight ,the ground sensing, bypass this items
The voice recorder start when the plane is powered
The thrust reverser is operative in ground and flight (is prohibited used in flight)