So normally the gust lock must be released early in the checklist, when the hydraulic system still unpressurized before the engine is started. Otherwise the gust lock will remain engaged until the engines are shut off again and hydraulic pressure is removed.
This strikes as a classic case for having a takeoff configuration warning horn fitted, as per most airliners. This would act as a back up to the other system preventing takeoff power being selected, which didn't work.
Part of the reason is that they did not discover the issue until after v1, when they attempted to rotate. Pilots are trained with the mindset that problems before v1 == rejected take-off, while anything > v1 means continuing the flight.
At the end of the takeoff/RTO brief it usually goes on the "or if the a/c is unsafe to fly." Even if >V1 this scenario seems to fit into this category. How long was the runway? On longer than required runways stopping after V1 is often not a problem; if you react soon enough. There might have been a moment of astonished disbelief frozen in the headlights phobia.