Sources tell The Athletic that the Philadelphia 76ers "ultimate purpose in the [James Harden] negotiations was to provide the Rockets with the leverage needed to maximize the return wit the Nets."
The 76ers had real interest in trading for James Harden, but Brooklyn's willingness to increase their offer reached a point where Philadelphia could no longer compete.
Sources also tell The Athletic that the Boston Celtics were involved in the later stages of trade talks as well.
Daryl Morey joined Philadelphia from the Rockets this past offseason and has a long relationship with Rafael Stone. With the 76ers and Nets sharing a division, Philadelphia benefits long-term from Brooklyn sending out the trade package they did for Harden.