Prior to the rise of synthetics, wool was in fact among your best outdoor-wear options. Military uniforms and mountain climbers would wear it. Even swimsuits and cycling shorts were made of wool, the latter through the 1970s (though spandex Lycra nylon was being introduced).

The transition point came in the 1950s and 1960s with the mass-marketing of synthetic fabrics and outdoor-wear, principally rip-stop nylon. Even then, a natural product, goose down, remained the preferred insulating material in parkas.

Until the 1880s, the only clothing materials that existed were cotton, linen, a few other plant fibres (jute, woven grass), wool, leather, silk, furs, and (generally for military use) metal.

In the 1880s, the first synthetics appeared: viscose rayon and cellulose (generally only used in collars and cuffs). In the decade of the 1930s, virtually all modern synthetic plastics were introduced, virtually all at Du Pont. Some of those saw introduction during WWII, though most didn't make widespread appearance until afterward.

The seismic shift in fashions from the 1940s-1950s to the 1960s wasn't just due to the everyday adoption of what had been working-man's clothing (denim blue jeans and cotton tee-shirts), but synthetic fabrics and dyes.

During the industrial revolution, it was thread-handling characteristics as well as cost which drove the adoption of cotton. Wool was too elastic, and tangled in machines (and was expensive). Silk was prohibitively expensive. Flax threads are insufficiently elastic, and would break.

Cotton threads were just right, and could be spun, spindled, and woven on early mechanical equipment. Cost was relatively low, and England / Britain has ample supplies from its colonies in Egypt and the Americas.

most wool pants are dry clean only. I actually don't know anything about the actual context of these pants when in use.

https://go-armynavy.com/military-surplus/collectibles/austra...

(I'm not vouching for that vendor, but I'm pretty sure that's what I've got. I got mine from ebay)