It’s an example of uncertified consumer grade equipment used in a commercial environment to disastrous results, outside of its original designed purpose. It’s one of the most well known examples of why you don’t use consumer grade hardware in a commercial/industrial setting.

It was not brought on board by the conductor or someone else, it was permanently installed in the train in place of commercial grade heaters they couldn’t source. It was installed in the wall during assembly.

I’d argue it is an example of cutting corners, they didn’t want to find / pay more for commercial grade heaters. It was not compliant with the original design nor fire safety standards.