I am not too sure how many correspondents in this thread have ever flown an aircraft, but the first lesson pilots learn, is that trimming the tailplane controls the speed of the aircraft. This trimming is either done at the front of the all moving tailplane with the jackscrew, or at the rear with the elevator.
Even in the simplest form of aircraft, a glider, you can bimble around for hours looking for thermals, with the trim set towards the rear, for 40 knots. But to give some increase in control for landing you actually need to speed up to 60 knots which equates to putting the trim just a bit further forward than mid-way. If you put the trim fully forward the speed will increase even further.
So The Lion Air pilots must have seen their trim going towards the very high speed end of the range, but unfortunately did nothing to disconnect the automatics, and fly manually. Maybe they thought if they switched off the electrics, they would also loose power to their trim switches.