My guess, based on the following passage, is that there isn't anything more to this than simple burnout, handled reasonably:
Hargrove first told Bavasi of his intentions June 20, after a six-game losing streak. The two then agreed to wait and see if Hargrove's inability to muster motivation for the game continued for a couple of weeks.
It did, even through Seattle's longest winning streak since 2003 . . Hargrove said he simply lacked drive.
Makes sense. Grover figures he can't go on any more come June 20th, but makes the very enlightened move not to make such an important decision during a bad run. Then, when things are going well -- eight game winning streak -- Hargrove still doesn't feel the mojo and therefore decides to call it a year or, possibly, a career. Athletes -- and despite a couple of decades in coaching Hargrove is still an athlete -- seldom exhibit such self-aware, deliberate decision making.
It's understandable that the media and his employers spent yesterday scratching their heads over Hargrove's timing, but absent some unlikely revelation, we should all be happy to see what appears to be a healthy balance of emotion and reason coming from a quarter where such equanimity is typically in short supply.
Good luck, Grover.