Old Ned wrote:
I knew about Cannondale's history. But there are other MTB makers (eg Kona?) who started making road bikes later?
Sure - Kona, Marin, GT and others were primarily mtb makers who added a road bike or two to their range.
I think a lot of the perception is caused by the fact that brands like Cannondale, Klein and Trek only started to arrive in Europe in large numbers when the MTB boom happened. European manufacturers had previously had their domestic markets pretty well sewn up, while the Far Eastern manufacturers had been getting stronger and stronger on exports to the US during the (road) bike boom of the seventies.
When MTBs arrived on the mass market, import channels that hadn't existed before were opened up, and companies that were known primarily for their mountain bikes began to bring in road bikes too, often selling them through new dealerships opened up on the MTB wave. As the big MTB boom began to cool off, more emphasis was put on other styles of bike, maybe giving the impression of MTB manufacturers turning to road production.