Funny, so did I. I would say that the DDs didn't come in to blow away the belt drives, they blew away the idler drive turntables. Within a very few years, Garrard and BSR were gone and Dual had migrated to belt drive and direct drive. The idler drive 'table was DEAD.
02-24-12: Mapman
FUnny, I used to sell many Japanese turntables back in their 70's heyday, both belt and direct drive.
I worked at the oldest audio chain in SoCal in 1975-6. We carried Garrard, Dual, Rabco, Philips, & Beogram. I remember that on FM stations I could actually hear the rumble of their idler drive turntables. The DD turntables were much quieter than those (unless you know how to plinth them) while still having that strong torque which BDs lack.
Some of the highly regarded BDs of the time were flaky. My sister bought two Philips BDs that didn't work right and took them back. She bought a Pioneer DD in frustration and it still works. And it's no doubt that when the Micro-Seiki's hit the market they were a force to be reckoned with.
Still, I think the virtues of BDs and the vices of DD are mis-identified. Yes, the Linn and AR TTs were belt drive, but they were also suspended. When you plinth and/or platform a DD turntable, the noise attributed (wrongly IMO) to the drive mechanism disappears. On the Technics DD 'table, the upper midrange glare is (wrongly) attributed to the 3.5 Khz servo, whereas damping the hollow aluminum tonearm makes *that* resonance disappear.
After 1985 or so, turntables didn't really fit into Panasonic's business model anymore, but they had to keep the 12x0 series in production because the dance club scene continued to keep them viable in the marketplace for another 25 years. Still, it marked the end of additional R&D expenditures related to audiophile playback. And that's all that's wrong with the SL12x0 series--other other audiophile turntables have 25 more years of development in noise, vibration, and resonance control, but they never improved on the torque or speed accuracy of the 12x0 series.