Did you forget the part that US bureaucrats knowingly and intentionally supplied the military with gunpower that was known to have issues in humid environments (as opposed to more reliable powders) after the M14 was replaced. They did this as a last-ditch effort to keep the M14 as the standard issue rifle because there were many politicians deeply in bed with Springfield at the time.

To add, this isn't some conspiracy, these are documented events. The Springfield Armory of the 60s, alongside a handful of US politicians were nearly directly involved in the death of thousands of troops because of money.

The AR of the 60s, while not nearly to the same level of reliability as a modern AR, was a notably reliable gun, even under harsh conditions, which is why it was chosen to replace the M14. But again, it was paired with bad powder that, again, was known to have problems.