The NBA is a player's league, or so it's said. That's not entirely true.
Specifically, the NBA is a superstar's league. In a five-man sport, a superstar is almost a prerequisite for a championship.
Defenses can scheme to take out the merely good players over the course of a series. To triumph, your team must claim a transcendent force.
There are only so many superstars, though, and a good many teams are left out of the sweepstakes. Pity to these lottery dwellers, for they're likely to go on for some more years with the absence of greatness.