The Nylon semiauto rifles (Nylon 66, 77, and Mohawk 10A) were a big deal when they were introduced, new technology making it possible to manufacture a rifle with a minimum of machined parts and labor. They were produced continuously for 30 years, a long life for any production item. The rights to produce the Nylon 66 and 77 were sold to a South American company who still produce the rifle. They were imported for a while but did not enjoy financial success, so my guess would be that after 30 years, the product was having a hard time being competitive with newer offerings.
I owned a Nylon 66 for about 25 years, got it used from a friend who got it so carboned up it took carburetor cleaner and solvent to free up the action. I really liked the light weight, but as with any lightweight rifle, accuracy can be an iffy proposition. My Nylon 66 never really shot all that well even off of a rest, but many people report excellent accuracy with them.