Apollo NASA is a main suspect here. I recall reading that long before the fire, NASA had seen that even asbestos burns in a pure oxygen environment. So there were grounds for concern and for engineering investigation.
Pure oxygen atmosphere is pretty dangerous. I worked with it at a steel mill where it was a process gas. Oxygen lines had to be "oxygen clean" before put into service. This meant no oil or grease or particulates that could strike a spark if propelled along the line. Also the line had to be sized for a maximum flow velocity or the oxygen would "scarf" the line. Think rapid oxidation like combustion.
I read a fatality report where a pipe fitter descended into an oxygen valve pit and burst into flames. The report speculated that the fitter had some grease on his gloves that spontaneously combusted in the presence of pure oxygen.
I suppose it's less hazardous at reduced pressure, but still not an atmosphere I would want to work in.
A search finds more info at https://www.eiga.eu/uploads/documents/DOC013.pdf which discusses this.