One chapter talks about Mattis, including various emails that were sent. He comes across as genuinely wanting to do the best thing for his men and hoping that Theranos could save lives in the field. There never were any field tests, because Mattis listened to his underlings when they said it would need to get FDA approval first. They then offered to let Theranos test random blood samples to validate the results but Theranos never took them up on that offer.
Basically, Elizabeth Holmes wanted to be a billionaire and restore her family's fortune. She started a medical tech company but didn't include any scientists or doctors on her board. Demos and employment were tightly controlled by NDA, and structured so as few people as possible knew about the scam. Somewhere between 1-8M (10-100%) of blood tests Theranos performed on hacked machines from other companies are suspect or outright wrong. Her company rode the "unicorn" wave at just the right time to get lots of funding and publicity, even though it has been operating since 2006.