There were a lot of potential trade packages floated for James Harden. The Nuggets were one of the teams in those discussions, in the hopes of bolstering their roster and hopefully making it to the NBA Finals. They already have a great young core, but sometimes, acquiring a superstar is the step you need to move forward.
However, it seems that the Nuggets aren't interested in acquiring a superstar if it requires them to give up their electric point guard, Jamal Murray. It makes sense, as they wouldn't want to give up a rising star who matches Nikola Jokic's timeline for someone who is getting older, even if it's James Harden. James Harden has been linked to many places, but he probably isn't going to go to Denver.
This decision seems good for the type of organic growth that the Nuggets have been building. They have built their franchise mostly through the draft. Besides their two stars, there are players like Gary Harris and Monte Morris, who they drafted, and eventually became elite role players. The Nuggets' franchise doesn't necessarily need James Harden: their two stars have the chemistry, their depth is good, and they could easily just elect to ride it out.
While James Harden is an amazing MVP caliber player, his chemistry with the Nuggets could be questionable. He could take away valuable touches from Murray and Jokic and hamper their continued potential development. Harden is a great scorer but is extremely ball-dominant. Perhaps another team who needs a lead superstar could trade for Harden: the Nuggets it seems, are staying put.