What? There was no compatible unit in the vicinity of Victoria station at the time? I realise this could have meant that another train might be delayed whilst the ECS is being used to effect a rescue, but as the only alternative seems to be to leave passengers on a train for 3 hours, I'd consider the use of another unit to be the lesser of many evils. If passengers had been told "don't worry, you'll be stuck here for 20 minutes, please stay put and don't try to get off" they'd probably have complied.
In the event, passengers now know that if their train becomes disabled in any way, they're likely to be stuck wherever that is for more an an hour (and possibly more) due to the railway's continual inability to learn from it's own mistakes. This makes them more likely to de-train themselves, thus putting themselves at risk and causing mass disruption to all traffic in the vicinity.
The passengers can't be blamed for having such a low opinion of the railway authorities to deal with what can boil down to very routine and avoidable incidents leaving them stranded with no heat, light or working toilet facilities.