Not having a great staff around him.
Detmer's offensive staff was awful. They were gone after 2 yrs.
Tuiaki's defensive staff was only slightly better but looked decent compared to Detmer's staff so they got more time.
Kalani's failure was not replacing the defensive staff much earlier. He kept giving the defense more resources but it didn't do any good. Tuiaki and Lamb were too set in their ways (or lazy) to change.
I do think though that he finally has solid staff's on both sides of the ball (although the jury is still out on AR's play calling).
Just my opinion.