Most people will say that this is par for the course. No harm done. It is just a difference of opinion. However, that is to ignore what it says about us and the way we view the world. This is particularly so for those who call themselves economists. Most economists believe that individuals do not make systematic mistakes (behavioural economists would disagree and point to a limited range of situations where individuals make systematic errors). Economists, even those of the behavioural type, must be surprised by the level of mistakes imputed to managers of sports teams. I'd imagine there are a fair few economists who regularly think that the manager of the team they support is selecting the wrong players. How does their view of sporting decision makers tally with their view of decision makers in other settings?
Rather than presuming that Louis van Gaal is making an error by picking Rooney, or Jose Mourinho is making a mistake in dropping Eden Hazard, we could presume they have more information than we do and/or are better at selecting players than we are. In these circumstances we might wonder what it that makes them select Rooney (or drop Hazard). Operating along these lines we might presume that Steve Hansen picked the correct starting 15 for the Rugby World Cup final. We might presume he was correct in not starting Sonny Bill Williams for most of the games that mattered. By contrast, Hansen always selected McCaw and Carter in the starting 15 for important games.
Hansen's decisions are questioned less because they won. Van Gaal and Mourinho are not having the best of times. But consistency, at least for economists, suggests we should presume the manager gets it right most of the time.