Optimism beyond the reasonable may be a critical trait for a successful CEO. Not necessarily what you want in your own manager, of course, but company leaders need to chase risk in order to do well and that's hard to do if you're ready to believe all the (reasonable) opposition that new ideas face.
Add survivorship bias to unreasonable optimism, and you get a culture of celebrating CEOs who demanded the impossible and got it enough times that the companies made money.
Meanwhile, CEOs who demand the impossible and don't get lucky are not celebrated, but are also not widely publicized as failures, so people don't learn from those lessons.
So there's the idea of 'depressive realism'. Basically, that depressed people may have more accurate judgements of the world than non-depressed people, since they're more willing to recognize the frequency of bad stuff.
I've always sort of wondered if there's a reverse effect - if the kind of person who can eagerly commit a big chunk of their life to a task with a 95%+ risk of failure is significantly less likely to be in touch with reality than others.
He was quite successful....
Any before anyone asks what the logic was behind this - there wasn't any - he just chose to believe it and ignore any evidence to the contrary.