Canon has done a better job than its competitors when it comes to marketing, and I think that they learned that from the AE-1 and certainly the Rebel with Andre Agassi.
Sometimes, it's not about whether you have a better camera. It's really about being able to sell your product.
For nearly all photographers in that era, the offerings from Canon, Nikon, Olympus, Pentax and Minolta (plus the others) would serve them well.
I had some friends who had the AE-1, and I always thought it was a very nice camera.