I think it was a chicken/egg thing. When the Taliban started spraying harassing fire at patrols from 1100 meters with PKMs there was a lot of hand wringing about the troops being unable to respond with their m4s.
This fed on the previous discussions about the limits of the 5.56 at long ranges in Afghanistan.
Then as we wound down the GWOT and pivoted to "Near Peer" the forecast was that Russia/China would field next gen level 4+ armor that could defeat 5.56 at any range.
This then created a requirement that our rifle defeat the armor at 600 meters.
The new requirement is enemy suppression at 1000 and effective hits at 600.
Here is one Congressional hearing about the "need", starring the ever stuck in 1969 MG Robert Scales addressing the shortcomings of the gas system, durability, effective range and varmint cartridge in 2017...
https://www.govinfo.gov/content/pkg/...5shrg34118.htm