Why is the ability to draft well probably the most important aspect of running a team?
Because it is a skill that deals directly with trying to successfully gauge the unknown.
It is much easier to know how good a player will be once he has played in the NBA. Of course the value of a player changes over the years, and hopefully he gets better as he matures, but even after only a few months of playing in the league most executives can somewhat accurately tell how good a player should be.
Before a college star plays a pro game this is a different story. It is simply hard to predict a specific future value for most of these college kids.
Even someone like Anthony Davis - who everybody likes and thinks will be good - has heard a wide range of comparisons regarding his pro potential. You can compare him to Marcus Camby and people will understand. You can also compare him to Tim Duncan and people will understand. The wide gulf of interpretation of a college player's potential leaves much to be discovered.
Obviously there is a gigantic difference between Camby and Duncan's pro careers, but right now we don't know which path Davis' career will more closely resemble. This uncertainty shows us how little we can know about college prospects.
By January of next year we will probably have a pretty decent idea what Davis' potential should look like, but right now we do not. It is hard to predict what exactly a player will turn into, even when we like him very much. It is always worth remembering that.
Often executives and scouts come up with general opinions of where a college player should be picked in the draft - a majority opinion - and "tier" the draft accordingly. There are players that are considered certain top five picks, other players who are likely lottery picks, others who are sure first rounders, etc.
This is how NBA teams make sense of the unknown. A general consensus among executives and scouts determines the expected order of the draft, and usually the actual draft order plays out the way this majority opinion expected it would. Nobody this year is going to draft Memphis' Will Barton before UNC's Harrison Barnes, even though there is no guarantee that Barnes will actually turn out to be a better pro. This is because it would be too contrarian towards the consensus opinion.
Theoretically the majority opinion of what the draft order should be helps fight against the unknown. What it indisputably does is help save face for the poor executive who drafts a bust. This reason alone leads to extremely similar mock draft orders being formed by most teams - if someone is wrong with a pick the reasoning can be that at least they were just part of the large majority that was also wrong.
The problem, every year, is that the consensus draft order is often incorrect. Many lottery picks turn out to be busts, while players picked late in the first round and second round often turn into very good NBA players. Some second rounders end up vastly superior to almost all of the guys picked before them.
So the NBA draft, no matter what they tell you, is damn hard to figure. That is why it is almost laughable when scouts get excited over a "good" draft as opposed to a "bad" draft (this year's draft started as the former and now apparently has become the latter.) The truth is we just don't know. It is hard enough to predict the future quality of even a few players in the draft, let alone the entire thing.
What a good NBA general manager should try to do is hedge his bets. Because the degree of uncertainty in a NBA draft is so high, it is best to always understand the element of risk involved when it comes to his draft choices. This is especially true with high draft picks. Top five picks can make or break a franchise. If you choose the right player you might have an All-Star for the next fifteen years, and if you screw up you end up with essentially nothing.
Therefore a good part of the NBA draft is simply risk aversion, especially with high picks. If you truly think a player will be exceptional it is important to take him, but it is maybe just as important not to take the wrong player. In many ways it doesn't matter if you're right - you just don't want to be wrong.
If this sounds confusing that is because it is.
If your team has a high pick you want to feel very confident that you are picking a guy who will be a productive pro. But the reality is always there: you can't truly have a good sense of what the player you select will end up becoming. At best you will have very auspicious signs of future success, but you will not know much beyond that (like in the case of Davis.) Sure things become busts, and lightly regarded second round picks become All-Stars. These things happen regularly.
Somebody who drafts well knows he doesn't know much. He is risk adverse, yet looks for value in every part of the draft. He understands there is nothing worse than squandering a high draft pick on someone who has incredible potential but fails to ever realize it, but he also understands that it is impossible to know for sure how good a player will be before he even plays a professional game. When analyzing the draft we should be using all the helpful statistical and scouting information we can find - and we should also realize that despite all these tools often working, sometimes they fail us miserably.
If you can draft well you are a good executive. The best way to draft well is to acknowledge the amount of sheer luck involved, and to also know there is still a way to work with that luck in an intelligent and advantageous way.