When I look at Theranos' board, I tend to think about it the other way around - Theranos sought out distinguished people that wouldn't be able to call them out on the science. Basically, that Theranos conned their board as well, and by picking distinguished, politically connected people, improved their ability to con the general public. That this non-medical board defended the company doesn't surprise me in the least.
So did loads of institutional investors - herd mentality. "He invested, must be good" and the other way round