I don’t know what sort of boiler this is, but designs I’ve seen have hundreds of small tubes. If the water gets low the steam can super heat resulting in an explosion.
For those few days.
That is why Steam Boilers are inspected annually at least in all the factories I ever worked at. We would break open all the control cutoffs high and lo, open up for tube inspections, firebox and burner and check all valves for leaks etc. Some of these boilers would be several stories high so it was a major project.
The ASME has been around for over 100 years and largely started because of boiler explosions. Over-pressure and -temperature devices are not rocket surgery and are required. Someone really screwed up on this one, I expect. It probably was *not* the boiler manufacturer.