History can be taught as 'kings, queens and their wars' or it can be told in terms of economic and social things. With the mountain biking craze not much has been written about why it did take off like it did - really very few people knew who Fisher, Breeze, Ritchey et al. were. People just wanted a mountain bike for some reason.
I also don't believe that these mountain bike pioneers were really that pioneering - since the invention of the bicycle people have been cycling off road and enjoying the thrills of descending at speed. It is kind of a natural thing to do. To a certain extent the bikes that came before mountain bikes - BMX - were off-road bikes albeit with small wheels although you could get medium flavour wheels with a BMX.
My revisionist view of the mountain bike craze is to see it as a natural reaction to what politicians, planners and motorists were doing to our roads. Back in the day roads were many times more deadly than they are today with country roads unrestricted so 'idiots' could drive them far too fast to possibly stop for any cyclists that might be using them. As a consequence, in the 70's and 80's roads were not at all safe for cyclists and the only cyclists that would use them would be doing so for reasons different to today.
As well as the instant danger roads back then were laced with deadly poisons from cars that are incredible to think about. Imagine putting lead in petrol?!? Who would have thought that was a good idea?
Cycling is enjoyable - that is a statement of fact. Cycling on dangerous roads is no fun at all (unless you really enjoy that, which I can understand). So mountain bikes came along and just filled a need for something that had been denied by the motoring thing.
Shimano did great things to get mountain biking started - they did a fantastic job of creating easy to service brakes, gears and other components. European component suppliers just did not get their act together which was their loss. Yet again, despite how wonderful Shimano were there were wider economic factors - the Yen was a fairly worthless currency at the time so Shimano parts were amazingly cheap given how high quality they were compared to their European counterparts.
The frames for the bikes and the bikes themselves tended to come from 'new' suppliers. Older brands that made 'lugged' frames lost out. The factories in the Far East (Taiwan) that had been built to TiG weld chromoly steel tubes were the ones making the mountain bikes. For them this was a natural progression from the BMX that had gone before. As contract manufacturers 'OEM partners' they took the brands that the likes of Fisher had started and churned out some real product, this being the right product at the right time.
Mountain bikes also rode on the crest of a wave of a consumer boom. Money was cheap and along with all the other consumer gizmos of the time, mountain bikes sold very nicely.
So, although the Marin County history is fun, the real story of why the mountain bike happened has more to do with the tragedy of the roads and economic circumstance at home and in the Far East.