Continuity mistake: Stock footage turns McGarrett's 1970 Mercury into his old 1966 model when he drives out of the Iolani Palace parking lot. (00:31:00)
Visible crew/equipment: When the bad guys pull up to the loading dock warehouse, the door of their shiny black sedan reflects several large round studio lights. (00:32:15)
Answer: He was fired. He never really appreciated his character. He felt Kono was portrayed as a big dumb Hawaiian and that the stereotype was racist. He also felt underutilized. He was fired after a heated argument with the show's publicist regarding his character. It seems there's not much details given regarding the incident or the firing, so it's seems possible he upset the show's producers as well.
Bishop73
No he said something derogatory about one of the Jewish producers that's why he was fired.