Good approach and I would add that the popularity of CX combined with Riv and Heine’s obnoxiousness were big early drivers here. Over and above all of that maybe a widespread sense of “holy crap there are a lot of cars on the roads and it would be nice to get away from them”? A ton of pro doping scandals making people disillusioned with road bike racing?
Disc brakes on non-mtb frames likely made it much easier for big companies to make such bikes since one could finally use wider tires and still allow for decent braking.
Here’s Fred’s epic post on vsalon:
Sounds like you are doing the hard work in putting together a framework @iwillbe
Maybe put it in a google doc and post it here with “people with link can comment”. Bet we could do a splendid job filling in gaps and making suggestions.