In the beginning, there was ONLY Armalite, Bushmaster, and Colt. That was back in the 80's and 90's. There were no other sources.
Today, Armalite is a Brand built by a different company, Bushmaster is a Cereberus subsidiary along with half a dozen others all built in the same Remington plant.
And Colt has to compete against FN and Remington for contacts because it's holding overseer is milking it for every dime they can get. It seems it barely got out of bankruptcy because of Sciens mismanagement. A more conservative Administration may have likely investigated on national security concerns.
Nope, what happened was a serious lack of capital reinvestment into the original concerns to keep their quality control up. With an open market with numerous competitors, the average buyer can get products that do as well or better. They have also learned that the military specification can be out of date or compromised by value engineering to prevent the contractor having to invest millions in new equipment. And specifications are just that - compromises.
So, now we get a lot more choices - from Armalite to Windham, and more. There are a lot who build and bid military specification, with more nimble corporate structures who can change their production faster with less expense to meet newer demands for different weapons - like 6.8 PDW's for Mid East security, or 7.62x51 rifles for a European NATO country's longer range requirement. They simply couldn't resurrect their old FNFAL's, and frankly they wouldn't have met muster as well. That water has passed under the bridge.
If anything, most of us avoid the ABC's now. Time passes, things change. What was the rule 30 years ago with autos or home construction is out of date now. Same with guns. There are some staple items that do well, but in the big picture it's different now, for good reasons.
My CCW gun is a 1911 9mm subcompact with no grip safety, my hunting rifle is a 10.5" AR pistol - and we discuss repealing the NFA. It's not 1985 anymore.