The key to the plot is not the typhoon but "...the financial difficulty of it, presenting also a human problem, [which] was solved by a mind much too simple to be perplexed by anything in the world except men's idle talk for which it was not adapted."
Characters surrounding the captain view him as a technically-able dullard, incapable of comprehending the little nuances and figures of speech within typical conversation. The character himself claims to not know what people talk about all day - surely they simply repeat everything time and time again.
When it occurs to him the barometer indicates a typhoon, his solution is to read a book on storms to extract advise. He rejects the advise on the basis it would put him two days behind schedule and hence not financially viable in spite of having a deck full of coolies. 2nd mate Jukes suggests the captain alters course - head into the swell - to make the coolies (and himself) more comfortable.
"I was thinking of our passengers, " he said, in the manner of a man clutching at a straw.Such a compartmental mind; if they are shipped in bulk - they must be cargo. It is so funny! I see this sort of thinking in my nephew and other literal minded people regularly and it pulls me up short, reminding me there are different world views I need to consider. Many teachers knock heads with such students and it is hard not to be offended by their perceptions. I just try to bear in mind that mine is not the only reality and sometimes their ownership of reality may be stronger than mine!
"Passengers?" wondered the Captain, gravely. "What passengers?"
"Why the Chinamen, sir," explained Jules , very sick of this conversation.
"The Chinamen! Why dn't you speak plainly? Couldn't tell what you means. Never heard a lot of coolies spoken of as passengers before. Passsengers indeed! What's come to you?"