NBA Playoffs. Rigged or not?

Year after year it seems there are a good amount of people out there who believe the NBA already has a plan in place as to who is going to win the NBA championship before the season even begins. Well i'm on the fence about this one because I am a Miami Heat fan and in game 6 of the NBA finals the San Antonio Spurs were up by fix points with twenty seconds left and the Miami Heat. If the NBA were rigged why would they allow the Miami Heat to be down by five point with so little time left. Ray Allen had to drain a three point shot with only seconds left in the game in order for the game to go to overtime. If the NBA wanted the Miami heat to win the NBA championship why would they allow that scenario to play out I just don't get it. Maybe I'm being naive because I don't want anyone to feel as though my team is being handed championships without having to actually work for them. Plenty of blood, sweat and tears get laid out onto that hardwood floor by my team before and even after games in oder to perfect their game. Now think why would the NBA want the 1999 shortened NBA season to be won by the San Antonio Spurs over the New York Knicks the mecca of basketball. New York is the city of dreams and it's where billions of dollars are made daily literally. Why wouldn't the NBA just hand the Knicks championships why would they want to see the Knicks lose season after season? I can't comprehend that at all. If the NBA is rigged it should always be in favor for the bigger markets because with the bigger market teams winning it means higher ratings and even more money being injected into the league. The objective is to compete with the NFL in annual revenue which they'll never compete with the NFL but if that's their goal why aren't the pushing for bigger market teams to win? Answer that question. Why would they hand Tim Duncan four rings when they can give Kobe Bryant three or four more rings in LA or give Carmelo Anthony a ring or two in New York? Come on people. Give me a valid point as to why the Boston Celtics only have one championship in nearly two decades. Give me a reason why the Chicago Bulls haven't won a ring since Michael Jordan left. You can't give me a reason because there isn't one to give.