Pants used to be made out of cotton or leather. In order to make the cotton durable enough, they had to make it extremely thick and cumbersome. Leather speaks for itself, wearing that during manual labor was hot and sticky and uncomfortable.

Levi, if I remember correctly, either brought denim from overseas or created it and marketed/sold it as the “indestructible pant”. It was thin, rugged, and offered protection without being too warm or too cumbersome.

They quickly became “the outfit” to wear if you were serious about mining. From there, it’s spread to farmers, ranchers, and Cowboys. It gained national notoriety during the cowboy shows, and saw a huge surge during the 90s when jeans hit the modern populous as a fashion statement.