From just before the dot-com bubble burst to when it had fully deflated, the tech stocks had lost some $5T of stock market valuation - in 2002 dollars. So no, it's completely feasible that there is $2.6T of hot air speculative investment in cryptos. In fact, considering how divorced from practical and technical reality all of the proposed crypto schemes so far have been, that sounds like a low estimate.

There is some value in providing shadow banking to the global criminal underworld, but I don't think it will be the next technological revolution.