My college roommate was convinced that Commodore would run off all competitors and dominate the market.
Was that the Commodore Amiga? The C-64 was a cheaper model that was great for entry-level programming and saving to cassette tape (in my case I saved to a 5 1/4" disk, perhaps because I was middle class with a front yard and everything LOL).
But the Commodore Amiga was geared more towards image and video editing. An editing software called Video Toaster was a professional level app that was used for some TV intro's like the graphics on Monday Night Football. Dick Van Dyke used Video Toaster to create the 3-D effects for Diagnosis Murder. So if your roommate got into graphics editing it'd be easy to see why he thought Commodore would dominate. If Commodore didn't have production problems, thus limiting supply, it's possible it would have dominated the graphics/media market. And the video and audio processing that made it good for video editing also made it good for video games for an out-of-the-box home computer.
I eventually got a Commodore Amiga when I got into college and needed an inexpensive computer that could emulate a PC for my computer science homework. I was blown away by what the video and audio processing could do for a home computer. I didn't get into that too much, though, because I expected there to be more of a market for back-end data processing.