Earlier quoted context omitted.
Although you make a good point about general portfolio diversification, the difference between a "normal" employee and a co-founder is fairly large in this instance. Co-founders are supposed to have confidence in the business they built - if they don't, why should other investors?
That kind of changes when one is forced out of the company.
I do hope that vengeful behavior like that would subsequently hurt one's ability to find investors for future projects. Unfortunately there is also a lot of that "this only shows that he is ruthless, we like ruthless" attitude in the world so I'm not sure that it would actually be taken as a negative signal. But that surely won't be an issue for someone with a reputation so firmly dialled in already as Kalanick.
On top of that, the idea of him going back to square one doesn't fit too well with the mental model I formed back when he was constantly on the news, I'd rather type him as the rare exception amongst founders who can easily leave it all behind and indulge in the spoils - but that's just a gut feeling of course, I know less about that guy than I know about some people who have been dead for more than a thousand years.