Put simply the Fire Brigade were apparently un-aware that the building's original safe construction ( as built ) had been altered so much as to make it so dangerous.
The only body who we know for sure had been warned of the danger, were the ministers with responsibility for fire safety via Building Regulations.
It is indeed very unsatisfactory, if not criminally negligent, that they failed to do the job they were paid for.
Perhaps it is pure chance that public discourse has been steered towards the fire service, and away from the Ministers who are truly responsible.
Or perhaps it's News Management.