The whole drift away from the 9mm was based on the 1986 Miami shootout. Bad guys getting hit with 9mm and not getting stopped. The FBI wanted to standardize .45 cal. but small stature shooters couldn't qualify. The 100 came along because someone said, "I know, we'll use a smaller diameter bullet." That was even harder to qualify with. Thus, the .40 was born. It's a great cartridge with a good balance of terminal ballistics and controllability.
IMO, and MO only, that if you can't hold a shooting standard, you need not be in a shooting job.
That said, there was a lot more about tactics, mostly lack thereof, that was the real cause of the 1986 debacle. Any time you put handguns up against carbines or rifles, you are going to suffer greatly. Which the FBI did. All the talk about which handgun is the best is useless if the shooters don't first learn to shoot at a high degree of competency and MOST importantly, learn how to tackle this kind of problem as a TEAM, not a bunch of individuals. Up-arming of access to carbines would have really been the discussion needed to have. Not which handgun round would be better suited to come up inadequate against bad guys packin' carbines.