The aircraft had and always has had kill switches for the trim system. In the first crash they were turned off per procedures and the aircraft continued to fly. They then put them back on and passed control to the copilot and the aircraft crashed. On the prior flight on that aircraft the crew had the exact same failure. They used the disable switches and flew the aircraft using manual trim to the destination without issues. In the second crash they were not used but the aircraft was still flyable. Neither pilot however noted or bothered to reduce power from full takeoff power. As a aircraft speed increases out of trim conditions increase.
Your 14 year old niece had more experience than the copilot in the crash. Things are done differently in Africa. I once had a Air traffic Controller admonish me after multiple radio calls he did not answer about bothering him while he was trying to sleep!
Here is a statement on his experience:
Two-hundred hours is extremely low," Aimer told Business Insider. "In an emergency, it becomes a problem. If you have a complicated airplane and you basically put a student pilot in there, that's not a good thing. Even if the guy in the left seat has so much experience, if you have so much imbalance of experience, that can be a problem."