Anyone who's ever piloted an aircraft would try to re-trim against pitch forces. It's inconceivable that the pilot for some reason just failed to do that. I'm not sure exactly what force it takes to get full nose up elevator at flying speed but it will be in the range of dozens of kilograms.

I personally wonder if there is potentially a thermal cut-off on the trim motor which could have been activated by this trimming and re-triming. Or even an outright failure of some part of the system.