Before vinyl, record discs were made of shellac, which is a natural secretion of the lac beetle. Southeast Asia was major source of shellac, but the Pacific war created a shortage of the raw material. Besides, shellac records were very breakable.
There weren’t a lot of plastics at the time. Celluloid could be used for records, but generated a lot of surface noise. Meanwhile, chemists were busy exploring ways to derive new polymers from petroleum and caol, and eventually hit on vinyl.
Vinyl chemistry is based on ethylene gas. One of the compounds you can derive from this gas is vinyl chloride gas. This was first turned into a solid polymer in 1872. But pure vinyl has a lot undesirable properties, so experimentation began to find a way to make it less problematic in production.
In the 30’s, Union Carbide developed Vinylite, which was a copolymer of vinyl chloride and vinyl acetate. It was formally introduced to the public at the 1933 Chicago Exposition. Vinylite was flexible, so it wouldn’t break easily. When it was eventually tried for records (around 1939), it was found to have better surface noise characteristics than shellac. That sealed the deal.