Being able to rationalize "why now?" is much easier after the fact, as the OP demonstrates with his list of his now-successful companies. Doing the same looking forward is much trickier.
I agree, and think the retrospective analysis on this is often really sloppy. In hindsight, the iPhone was clearly at the right time, and the Newton was clearly at the wrong time, but the track record of anyone distinguishing between those is very poor. Even Jobs, famous for some of the big wins on that score, was wrong about timing as often as he was right (e.g. NeXT was about as timely as the BeBox with its initial launch).
I agree, and think the retrospective analysis on this is often really sloppy. In hindsight, the iPhone was clearly at the right time, and the Newton was clearly at the wrong time, but the track record of anyone distinguishing between those is very poor. Even Jobs, famous for some of the big wins on that score, was wrong about timing as often as he was right (e.g. NeXT was about as timely as the BeBox with its initial launch).