Atari like Commodore didn't market their new systems that much. It was mostly magazines and word of mouth. At least in the USA it was that way. Still they both controlled the home computer market in the 8 bit areas.
Atari's dominance is a major factor of the video game crisis in the 80s. The home console industry almost collapsed because all the consoles were licensing without quality control. Games would be broken or just badly designed for full price.
It's archaic now, but when the NES came that golden "Official Nintendo Seal of Quality" saved the industry. Amazingly, the Nintendo CEO who was granting this seal did not play video games. He would have an employee play the game in front of him and he would decide whether it was a good game or not.
It's also worth noting that this crash was largely North American, as the European gaming market was dominated by home computers.
If you have any experience with home computer games of that era, you'll know that the quality control wasn't actually better, it's just that games came on cassette tapes and floppies, and so were vastly cheaper mistakes when you bought one (plus you could fix the bugs yourself on the ones written in BASIC, fun!!).
