I don't she meant to suggest that improper cooling led to the warehouse burning down.
She implied that DC are built underwater/in mountains (true) often (false) because electronics get hot (true...ish). And then drew the conclusion that this is one of the reasons the warehouse is cold (false) on top of the obvious one:
> The temperature was to protect the cold food, I was told.
As you say, it's total nonsense - even if the cause does turn out to be an electrical fire, it's unlikely to be due to insufficient cooling of the whole warehouse.