Asbestos was good at many things. It could add strength to cement–its tensile strength is greater than steel–yet its fibers could be woven into cloth, and made into fireproof gloves for handling hot equipment.
No single material could replace asbestos in all its applications. This versatility was complimented by how cost-effective asbestos was.
Part of the reason asbestos made so much financial sense versus potential substitutes were the conditions under which it was mined. Cheap labor and minimal or nonexistent safety considerations meant asbestos was inexpensive and garnered substantial profits.
Major asbestos companies like Johns-Manville not only used asbestos in their products, they also owned the mines. While asbestos mines were not their only source of income, they were particularly profitable. Johns-Manville, for instance, enjoyed profit margins in their mining division two or three times higher than the profit margins for their other divisions.
Had the health and safety of workers and the treatment of their medical issues been factored in, asbestos may not have been considered cheap, or even cost effective.
While a fraction of the amount that used to be imported is brought in to the US today, it is still a lot of material considering the risks of mesothelioma and other asbestos related diseases.
The longevity of asbestos on the market can be tied not just to its fire retardant, lightweight strength, or insulating properties, but also to the profits of asbestos mining companies, many of whom pushed the cheap and widely available mineral into products they also produced and sold.