Well, from one perspective, each of these failed companies could have been testing their own "sustainable competitive advantage" thesis. A thesis that turned out to be incorrect. After all, you don't know your sustainable competitive advantage really is in fact sustainable and and a competitive advantage until you win. (e.g. Google. They were just another search company, and one that could have failed like so many others.)
From another perspective, each of these companies is wandering through, as the author puts it, the "wildernesses nobody knows" looking for opportunities and either didn't find one or weren't able to grow that opportunity quickly enough.
Some say we're in a bubble. Others say we aren't. Frankly, I don't give a damn. I just see that there's tons of innovation being funded. Some innovations may be evolutionary, others may be revolutionary. Funny thing is: you often don't know what will be evolutionary or revolutionary until you try.
I'm glad many people are trying.