Theranos was worth $9B in 2013 money, and it latet turned out that they had literally nothing but hype. Enron was posting $100B revenue the year before it went bankrupt. Bernie Madoff's fund had huge banks as institutional investors. Magic Leap was valued at $4.6B and had some purportedly amazing demos behind closed doors that anyone who witnessed them thought would revolutionize entertainment.
While these are not necessarily typical cases, they show that it's absolutely possible to have gigantic valuations raised from industry experts with nothing to show for it, if you're good enough at lying.
The weird thing about Theranos is that every single expert who knew about the technical details of blood testing basically called out the BS from the get go.
Blood testing for a single condition can involve blood separation via centrifuges, application of various chemical solutions, a multi-step process using varios test strips (each with different specificities/sensitivities). Not to mention some of the offending markers might be so rare in blood that you'd have to draw multiple vials just to get a statistically significant amount of markers.
Reducing just a single one of these tests to an instant test that works with a drop of blood would be a major breakthrough, subject to various medical awards (and lengthy medical trials).
Well, in this case, no one knows the technical details.
Theranos famously didn't manage to raise VC money, the funding all came from people like Rupert Murdoch and the Walton family.
That makes a lot of sense. VCs only make money when companies go public, so a medical device that requires years of regulatory compliance legwork to even be allowed into a lab or pharmacy is an immediate no-go.