Why was asbestos used so extensively if it is such a hazard?

The asbestos minerals ability to resist high temperatures is what made it so useful. Asbestos is ideal for any process involving the conservation or preservation of heat. The fibre gives protection against fire, corrosion, cold, acids, alkalis, electricity, noise, energy loss, vibration, salt water, frost, dust and vermin. For a long time the dangers of asbestos use were not widely understood. Asbestos related disease generally takes many years - often several decades - to develop after exposure. Thus, the scale of the health risks were only becoming known after asbestos had already been widely used and many people had already been exposed.