Asked by Charles on Patreon:
"I'd love to hear you do a deep dive on the commissioning and procurement process of the Chauchat compared to the FAMAS or the HK416F (or the STEN and the L85, PPSh41 and the AK-12 etc). The specific question to answer would be: 'why does defense procurement take so much longer and cost so much more today than it did in the first half of the C20th when national defense was a far more pressing concern?'"

I think there is a misunderstanding in the core question, because small arms procurement a century ago was every bit as complex and costly as procurement today. In fact, trial a hundred years ago often involved many more type of guns, because submissions were taken from individual inventors with the expectation that a winning design would be produced by a national armory. As such, submissions did not have to be limited to companies capable of mass production.

What does make a big difference in procurement is the different attitudes between wartime and peacetime. Both he Chauchat and Sten were adopted during wars, as types of arms that were deemed immediately essential. As such, the standards for adoption were relaxed from "what is the best thing we can develop for out military" to a much more short-term "what will fulfill this specific need as quickly as possible". In both cases, the resulting guns did the job that was needed, but the abbreviated development process resulted in significant flaws that led the guns to be quickly replaced after the war was over (the Chauchat by the Chatellerault 24/29 and the Sten by the Sterling).