There is Zeitgeist to be considered, the UK was heading into the World of the MC, these were being heavily covered in the Mainstream Media, I myself was drawn in and even bought Demo' models from a particular HiFi Magazine.
There was a growing trend being generated toward MC's from the Market Leaders. Others competitors were no doubt in the wings sharing an interest in benefitting from the growing trend.
A Tonearm Producer did not have to express any great interest in a particular Cart' design, the changes were occurring very very quickly and they were riding on the wave of interest. The MC idea has stuck to this day. Most with an interest in vintl replays have the underlying idea a MC being selected is a step forward over the alternative designs.
Linn were commencing to supply a range of MC Cart's, with the the Ittock as a Tonearm.
Roksan and Audio Note and I am sure a few others also produced a MC in this period. Goldring came to the market a little later.
With this homebred interest, there was inevitably the extension to the Japanese, Scandinavian and other European Countries offerings.
The Cast Singular Arm Tube with a Formed Head Shell become the Tonearm of choice to exploit the encounters to be had, very rarely was an other type seen used in the media and at industry events.
The Rega Design sold like hot cakes, I believe I have seen 400 000 models were sold over not too many years.
SME, Linn, Roksan and a search will find others that during the 80's had produced new Tonearm Models with a Cast Singular Arm Tube or Singular Arm Tube and formed Headshell.
Later others come forward with the same design types using modern materials such as the WB- A.C.T One.
Statements like the Rega has been inferior are not entirely accurate, there is way too much info available to suggest differently.
My view on the design and its variants being much of a muchness stands, as this is the result of a broad range of experiences of these design types.
The Korf Blog has put the RB 300 through the wringer and it stands tall, interestingly the formed Headshell is seemingly the most obvious weakness when assessing measurements taken.