I guess I misunderstood slightly...
There's no denying the revolver was king in America during the 20th century. And its because of the fact that compared to the semi auto they are just so freakin' versatile. Not to mention the tremendous head start.
I grew up, and grew into handgun shooting in an era when hi capacity was the Browning Hi Power with a huge 13 rnd magazine. Firepower wasn't at the top of the list of desirable things in a handgun. And the 9mm Luger was not as good a performer as it has become today.
Magazines for the .45 were 7rnds, not 8, and there was endless debate on the real world advantage of the extra 2 rnds possible in an auto pistol vs a revolver. The 9mm vs .45 debate kept us entertained for several decades before the 9mm came to be accepted as adequate in most people's eyes, including my own.
The handgunning world in the US has changed a lot since then, and in many ways become more like Europe, just as our nation has become more like Europe in several ways.
The 9mm bacame the free world's standard due to its adoption as the Nato round, and agressive marketing, as much, or perhaps more so, than because of the capability of the round itself. One of the reasons the .45 didn't get adopted by a lot of other nations is that we didn't push it. Not to anything near the degree the Europeans (Germans, primarily) pushed the 9mm in the world markets.
Face it, if you are a govt, looking for a pistol, and its got to be an autopistol (and after WWII, everybody decided the auto was good for military use), then it comes down to only three choices. The US .45, the 9mm NATO, or something else, like some oddball round locally produced, or something from the Soviet bloc nations. By the 80s, the US went to the 9mm, the oddball rounds were few, and the Soviet bloc was coming apart. Today, its even simpler. IF you want a pistol you can support easily, it comes in 9mm.
As a civilian, if you want an effective autopistol, 9mm is the base minimum, provided your local laws allow you ownership. I'm not talking pocket pistols,and people will argue the .380 is effective too, I'm talking about a full size duty class gun, and for that, .380 is a waste, because you can get 9mm.
Notice nobody talks about the 9mm for hunting. Handgun hunting is primarily a US thing, and for that, revolver rounds are clearly better than the usual semi auto pistol rounds.
Getting back to the OP, the base reason the 9mm is so popular in Europe is the same reason the .45 is still so popular in the US. It came from there (history), it works, and there are lots of choices available.