I asked Dave King, a credentialed blogger from Bright Side of the Sun who witnessed Hunter's ascension and struggles up close, for his take on the situation. His response appears below:
Hunter was totally unprepared at midseason when he was tabbed to take over the Suns. Gentry's top assistants left when Hunter took over, so Hunter promoted Igor Kokoskov to lead assistant and found two other organization guys willing to sit on the bench with him. This isn't to rip Hunter at all. The GM burned the bridges and put Hunter in charge, so it wasn't surprising Hunter had to find a new staff right away from table scraps.
He never coached on any level, so he didn't have a real plan on offense or defense. He slowly modified the schemes - defense first, then later a bit on offense. While he replaced the entire defense, he had his lead assistant (Igor Kokoskov) call all the plays for a few weeks. He did most of his work in practice and setting accountability standards for young guys - fining them for not paying attention to coaches, calling them out privately (and later publicly if that didn't work) - and installing a defense he liked better. Eventually, he took over offensive playcalling but said he would totally re-work the offense if he could, but didn't have time.
All in all, the bottom line wasn't bad -- which says a lot (I think) about Hunter's potential.
Gentry went 13-28 playing best combo of veterans he had, even enjoying perfect health through 41 games.
Hunter started 8-13 even though he was revamping the schemes and playing younger (less productive, consistent) guys. But when the starting center went down (Gortat) and the backup got gimpy (O'Neal), Hunter went only 4-16 the rest of the way while playing even more young guys.
The pluses: 8 wins against winning teams; a better defense under Hunter than under Gentry despite Hunter missing his pivot men
The minuses: a franchise record number of 25+-point losses in only half-season; a much worse offensive efficiency than Gentry was able to muster.
In summary, Hunter has the potential to be a good coach if given time to put together a real solid staff and install his own schemes in the offseason and training camp. Skeptical veterans were disappointed in the season, but still thought he might turn out okay if he stayed in Phoenix.