That's a subjective view in hindsight but remember that Nikon and Canon were the last of the major Japanese manufacturers (of the era) to release an SLR (both in 1959) and that was probably an advantage although Canon made a poorer start. Pentax were the first company to sell 1 million SLR's due to the success of the Spotmatics. Also remember market share differed across the world.
Originally Posted by CGW
The first SLR system I came across was about 1964 and I can assure you that Spotmatic system was very comprehensive. In the UK Pentax had an advertising campaign based around many well known professional photographers well worn but still fully functional Pentax Spotmatics, and they preferred them to Nikons.