I don't recall even hearing the term "wonder nine" until maybe 1979 or 1980, even though the S&W Model 59 had been around for almost a decade by then and others like the CZ 75 had been out for about 5 years or so.
I was required to carry one of the .357 Magnum revolvers on the approved list, and I chafed at that since I would have preferred to carry a 1911. I loved the Hi Power as well, but 9mm hollow point performance in general at that time was very poor and I had no desire to carry it, or a wonder nine, on duty.
For example the IL highway patrol was using 9mms in the early 1980s and had some notable failures with Winchester's 115gr Silver tip, which was the top performer of that era. One instance involved a biker who took 15 hits and kept going to his bike before he was finally stopped. Another IL highway patrol instance involved a suspect on PCP who took 33 rounds of 9mm before a before finally being put down with a 12 ga.
A couple years later, one of the factors that was identified in the 1986 Miami shootout was the poor performance of the FBI's 115 gr Silvertip load, failing to penetrate enough to stop one of the shooters, when their .38 +P LSWCHP load would have done the job. The FBI switched to a 147 gr subsonic load, and it was also a poor performer as it under expanded and over penetrated. They then over compensated with the 10mm, before backing the load back down to reasonable levels (which led to the development of the .40 S&W).
Some departments in that era also issued 9mm FMJ ammo and it was notorious for not only failing to stop assailants but also massively over penetrating and creating additional risk to bystanders.
So yes, the technology was there in terms of double stack SA/DA 9mm pistols, but the technology in terms of effective 9mm hollow points was severely lacking. That more than anything else kept a lot of the wonder nine "dreamers" from actually carrying one.