In my opinion one of the biggest catalyst for change was brought on by the Miami shooting in 1986. The FBI "research" that followed was latched on to by the gun writing world and this was largely due to the fact that the gun writing world was who the FBI sought out to help with their "research" and development of newer, better, duty weapons.
Savvy lawmen did use and love the 1911 and Browning Hi-Power for years but these were mostly relegated to real professionals that belonged to departments or agencies that allowed for such things.
The idea of giving a 1911 or Hi-Power to large departments would fall pretty fugking flat and for good reason. Firearms training for a lot of departments consisted of nothing. I know a guy that took a job as a "summer cop" in the early 80's. This was very common in a lot of towns and cities back in the day. His duty sergeant literally dug around a desk drawer and handed him a Model 10. Then he dug around the pen drawer in the middle of the desk until he found six rounds to give to the "summer help."
As Mackay mentioned, most people don't realize just how incompetent a lot of law enforcement were when it came to firearms and tactics. It was not uncommon in the 70s and 80s for a Chief to forbid the use of speedloaders because they didn't like the aesthetics of the pouches on a duty-belt. There were even places that an officer on probation could not have more than one reload on their belt because they had not yet "earned" a second reload. LOL
Another one of the biggest turning points in firearm culture and training in law enforcement has come from the Afghanistan and Iraq wars. A lot of the professionals came back and found careers in teaching, and that teaching was rooted in hard reality. Add to that, that we have the internet and all these combat vets with real world experience can now find out what you really are or were and call you on your bullschit. It has gone a long way toward killing the old and absurd cultures that existed in law enforcement for decade upon decade.
It's actually a pretty fascinating topic when you really start to research it.
