When the military forces were first inflicted with this mess, it was because of GREED. Historically speaking, as a general rule, the desires of the combat infantryman are passed over to meet the greed of the politicians and gun makers.
Actually, this is completely incorrect.
I suppose you are trying to suggest that the AR-15 was some sort of corporate scam by Colt inflicted on the US military.
But, that has nothing to do with 5.56mm. The cartridge was developed based on US military analysis of battlefield realities, and the existing AR-10 was adapted to the new army cartridge because everyone with anything more than a tenth of a clue had figured out that by the 1960s the future was in getting away from the failed 7.62x51 service rifle cartridge as fast as their R&D budgets would carry them.
Of the 3 recovered enemy dead, we found that all 3 had been repeatedly hit with small bore .223 caliber bullets. We also found out that all 3 were stoned out of their minds so that pretty much nothing would stop them.
So if they were dead, how did anyone know if they were under the influence of something? Much less make an assessment as to their level of impairment? Was MAC-V running a medical examiner's office and doing autopsies? Haven't heard about that before if they were.
Documentation going back to the days of the Filipino Insurrection, the Korean War and WW2 shows that our weapons SHOULD have been designed to be used against doped up or highly intoxicated enemy troops. That was why the .45 acp pistol was designed and we lost track of that "little fact." The M-16 should have been designed using a bigger diameter and heavier grain bullet.
45 ACP was adopted because the US military adopted a service pistol firing a cartridge that was down below 380 ACP power levels. Mythology aside, it did not prove itself to be an especially effective man stopper, even if it was better than what post dated it.
Now as for intoxicated or doped up soldiers -- frankly if I had the choice I would always prefer to have any gunfight I was involved in have the other side half or more in the bag on booze, pot, or heroin. The solution, in those very rare occasions when it's an issue (because it isn't terribly common) is what LE figured out a long time ago, but the military has been very poor in prepping service people for -- keep going after them until they are dead.
In another combat operation I saw one fellow paratrooper dump a magazine into an enemy soldier who was walking towards him. The enemy soldier ran off leaving behind a blood trail in his wake.
And in another combat operation a guy I know had a face to face encounter with a bad guy (Afghan flavor thereof) and killed that guy with a single round of 5.56mm to the COM while that guy was trying to get his AK pointed back at him.
Anecdotes aren't statistics.