It took them a while to diagnose it as the cause of lethargy and training problems that he had. He suffered again this year. I think that before the Vuelta, Sky weren't intending to renew his contract. So there is a good chance that graph was made with data that doesn't represent his healthy performance level.
Exactly. If you know Froome's history it's pretty easy to see what was going on here - with hindsight. Brailsford thought he was dealing with someone who was never going to realise the early potential that has been spotted (by Shane Sutton, incidentally), whereas he was actually looking at someone suffering from the debilitating effects of an as-yet undiagnosed and certainly not yet treated illness from which he would recover. I am sure if you looked at DB's equivalent graph a year later it would look rather different. Overall, his approach looks like common sense, really.