Simple -
it's one game to them.
If directives come down for teams to take a dive, then they simply get one back later on to even up.
On a simpler level, the Nuggets players simply didn't care about the game as much as the Kings' players did.
But this one game was absolutely vital for Vivek, Vlade, the entire Kings organization to save face and not lose MILLIONS of dollars with immediate proof of how hapless the team is now.
From a business standpoint, it make business sense for the NBA to have the Kings have that one game (with all the attention and eyes on it) to let them shine and not completely turn-off the fanbase.
People will have that as a mirage to keep their hopes up for a long time, and they will bank on that (market) "the up-and-coming, promising youngsters" angle.
THIS game is much more reality of the NBA.
Whether you want to explain it through a conscious conspiracy (keep in mind the defense the Kings got away with which fueled the offense which is very rare for them not to be called fouls), or a simple reasonable difference in how much each roster needed the win, the result is the same -
last game was a mirage, and this game is more the reality of the Kings for the foreseeable future.