The story has always been that it was a NATO compliance thing, and I tend to agree. The M9 was adopted back in the 80s when women were still a much lower % of the active force, and if the M9 was more compatible for females due to lower recoil, it was more problematic for them due to the larger/fatter grip. Furthermore, the M1911A1s in the inventory at that time were pretty ragged and worn.
What have heard, and do believe is that the FBI's short-lived affair with the 10mm was in fact based largely on the inability of the growing number of female agents to tolerate the recoil of full power loads.
I was a liaison to the Joint Service Small Arms Program (JSSAP) at Aberdeen in 1978 when they were really pushing the 9mm as the new “Personal Defense Weapon” to replace the .45 and the USAF .38 special.
Some of the discussion was about “NATO commonality” and there a lot of cooked studies about 9mm lethality but the discussions also mentioned the difficulty women and “men with small hands” had with using the .45.
We Marines were strongly in favor of keeping the .45 but the army and Air Force strongly pushed the 9mm and specifically the Beretta 92 - to the point that when Colt, S&W, H&K, and others started to conform with the requirements, the army would modify the requirements to more clearly to match the Beretta, moving the goal posts.
Being a smart ass captain, I raised my hand and asked “sir - is that the same 9mm the Germans lost two wars in a row with?”. The army colonel in charge of the briefing told me to shut up and sit down, while we Marines laughed.