I know exactly how that explosion in development happened. Originally, electronic music was viewed as a purely academic thing, and the majority of the R&D was being done by/for academic musicians and composers. One example that I can think of is the scanning polyphony method that E-Mu licensed to Sequential for the P5...the initial stab at that was done right across town in Urbana by Jim Beauchamp back in 1964. From that sort of research, it made its way to E-Mu in the early 1970s, was refined further, etc.
But what happened is that the focus for synthesizers changed from academia to pop. When it was obvious where the money was, synth companies changed their developmental paths from the academically-driven aspects to ones that were more aligned with working musicians. The annoying thing, though, is that while some academic studios were able to incorporate new developments alongside the older ones, many hide-bound academic music departments remained hopelessly stuck in their grant-writing cycles. This isn't where you want to be looking for new ideas if the objective is to create instruments for working stiffs, so by the mid-1970s, academia was just about DONE in terms of relevance.
In fact, I can cite a first-hand experience with this. Back during my undergrad, both I and my comp/theory prof "got it"...he was adamant that the future would be software-defined instruments, and I was working on adding relevant tech to the electronic music studio at MTSU (I opted to add a Memorymoog for starters...VERY smart move at that time). So when I got to Illinois and profs and grads were jizzing all over the creation of the hardware-dependent Kyma system...I knew in a flash that this was some VERY loud barking up the wrong tree! And while Symbolic Systems still puts out their DSP farm-reliant Kyma system for thousands and thousands of dollars, any one of us can go and buy an iteration of Arturia's spot-on Synclavier VST (no, really...it's PERFECT now that it has the resynthesis function), load it into the DAW of our choice, and wind up with what's essentially a bespoke Synclav Post-Pro system for a few hundred smackers! Would this have happened if, say, Michael Jackson hadn't made the original Synclav's sound an iconic part of "Thriller"? Probably not!