I’ve only managed to see this episode once, but something I didn’t understand was Spock’s decision to try and hide in the debris field. At this point they believed the planet was the source of the problem, but it seemed mostly a guess that the debris field might shield them.
Wouldn’t the most logical action have been to get as far away from the planet as reasonably possible until the effects appeared to subside? I know Una made a point that they had crew down there, but it’s not as if they can’t return more cautiously and with a clearer understanding of what’s happening. You’re also helpless to help your landing party if you’re completely incapacitated yourself.
We do know that the first landing went wildly wrong quickly. It’s possible that the judgement and short term memories of Pike and Spock of that landing were affected by more than trauma and shock.
There was individual variation in how rapidly the effects presented. We saw that La’an experienced some early tinnitus shortly after the shuttle landed.
On the ship, Spock wasn’t necessarily correct in his inference given he was already experiencing some cognitive impairment by that point.
I think it’s not just because Una pointed out there was crew down there but specifically told Spock they had to (should) stay close. He took it literally as a command whereas he really should have evaluated it for himself.
He recommended to the First Officer that they retreat from the planet and she gave him an order not to do that. She went to sick bay after but I don’t think command was formally transferred to him.
So he looked for an alternative that would keep them safe while still executing a superior officer’s instructions, and he got it wrong by misunderstanding compounds in the debris that he’d never encountered before. If he’d been right about the debris it would have been a genius move. As it was, he followed orders and looked for non-suicidal way to do that.