I don’t think some people really understand that a passenger railway is transporting humans, not inert robots.
Three hours, yards from a station, is bound to cheese some people off. Three hours with no toilets is going to result in someone needing to go. At three hours with no light or heat in this weather, on an apparently crowded train, it's a miracle there were no major medical emergencies. I've seen one report on Twitter from a lady who used a towel to hide the fact she was having a panic attack from other passengers (because hysteria is contagious.)
It's all well and good to say "it's dangerous" and "it's illegal," but if they think they might be in for an overnight stay on a packed train with no toilets or heat a la the New Forest incident, can you blame them? Especially if they were told the power was off because people were walking on the tracks - meaning they knew it was safe?
I know I sound like a stuck record but this keeps happening, and the relevant parties need to get their acts together and understand that in situations like this, people will self-evacuate.