Back in the day, the Canonet was going out of the shops and making pictures, and not coming back for repair. It earned a reputation as a great camera.
It was a well known bargain.
As a camera seller way back then, it was a no brainer camera to sell. EVERYBODY could use it, it never failed, and everybody loved it. It was just the right size. And if a customer couldn't afford it, or didn't like its complexity, or just wanted a smaller camera, there was the Canonet 28 ! Both used the flash that coupled to the focusing. Worked great.
Remember these things didn't start out as desirable: they earned their reputation.
It has an accurate rangefinder, reliable shutter, good metering and an excellent lens. The quickload system worked very well. In communities where B&W photography was done, it became a proven, inexpensive camera. And as films improved, the camera just got better.