Kirk was also an idiot telling Sulu off for some comment he made. Perhaps he was feeling guilting about an inappropriate landing party configuration.
You keep saying that but I didn't get that at all, can you say what it was?
Was it this part in the beginning?
KIRK: For one thing it means we're stranded.
SULU: The Enterprise must have blown up. That would explain the high radiation readings, wouldn't it, Captain? If the matter - antimatter engines
KIRK: Shall we stop guessing, Mister Sulu, and try and establish a pattern? I get no readings of high energy concentration. If the Enterprise had blown up, it would have left a high residual radiation.
MCCOY: Could it be the Enterprise hit the planet?
SULU: Once in Siberia there was a meteor so great that it flattened whole forests and was felt as far away as
KIRK: Mister Sulu, if I'd wanted a Russian history lesson, I'd have brought along Mister Chekov. This is a matter of survival, gentlemen. Without the Enterprise, we need food, and we need water, and we need them fast. I want a detailed analysis made of this planet, and I want it now.
SULU: Aye, sir.
That's my best guess of what you might be referring to and I don't find that to be a jerk or and idiot.
It didn't reflect well for Sulu, either, just guessing things without analyzing the facts or prioritizing his duties.