I don't know the reason for Jack going to the competitor. But I think it's safe to say his vision consisted more of very aggressive business decisions than of great ideas. A team of engineers invented and proposed the C64 design; specifying the amount of RAM, which CPU to use, or buying an OS/BASIC doth not an engineer make.
Without visionary engineers, a cheap powerful computer would simply not have been possible at that time. Jay Miner's vision reached farthest, while Tramiel's vision reached for "Rock Bottom Price".
This is no disrespect for Jack Tramiel's achievements at all - going from nothing to an international business superpower is a trait to be envied, not least by me !