This was an industrial accident and had very little to do with "spaceflight". The nitrous oxide is used as the oxidizer for the synthetic rubber fuel for SpaceShipTwo and is carried in a spherical tank. Nitrous Oxide is stored as a liquid at about 750 psi at ambient temperature.
It is stored this way whether being used to charge cans of whipped cream, as "laughing gas" for anesthesia, in drag racing (other major uses of NO2) or as an oxidizer for a rocket ship. It looks like the tank ruptured. There may not have been an "explosion", only a pressure vessel rupturing with reslting catastrophic consequences. Think of a SCUBA air tank rupture, but with less pressure.
No, it was not astronauts that died.
But it was people working to put them up there.
A big part of that is “industrial” kind of work sure.
No less necessary then anything else involved.