A lot of it is just PR. The Diamondbacks have spent years billing themselves as a contender, despite that they've been generally a bad team for 4 years and a few years of that they were grossly incompetent. However, their PR department is very effective at reaching the fan base, much of which was in denial over just how far the team actually was from contending for anything (national writers meanwhile had been trashing the team's moves for years).
The Suns level of success is similar to the Dbacks over the last few years, with the exception of the surprise 48-34 season but the team is absolutely horrid at marketing itself. "Ignite the future", "All for Mook", "Team FOE" (yes they had the Morris Brother's stupid motto on a banner). Bad stuff.
The Suns are a true star player away from contending, the Dbacks need an entire pitching staff. Essentially, both are in similar boats (but the Suns will probably have a better winning percentage), but one team is near the top of this list, the other near the bottom. Sure, the Dbacks offer a cheaper night at the park, which they should be commended for, but the divide in this ranking is much larger than simply that. The Dbacks sell themselves much better than the Suns do. Almost as badly as the Suns need to improve their product on the court, they also need to can whoever is in charge of PR and marketing and running the nightly experience of the Arena (outside of the game itself). The Halloween colors, the endless droning of "D-FENSE" over the speakers, music blasting during every stop in play... its ugly.
