[PP+ Question] The slower-learning monkeys ( TC question)

The slower-learning monkeys searched ___________ but unintelligently: although they worked closely together, they checked only the most obvious hiding places.

❑ competitively

❑ impulsively

❑ cooperatively

❑ deviously

❑ craftily

❑ harmoniously

I got the answer right. But I was wondering that how although here didn’t affect the logic in the first part?
Is the ( : ) stronger than although? So, it gives us that the two parts are = ( disregarding although )

although establishes a contrast with the latter part, namely that they checked only the most obvious hiding places (implying that they were not particularly intelligent). Thus, the two sentences divided by the “:” parallel each other. Harmoniously but unintelligently : worked together but stupidly.

Greg mentioned in some TC videos that if we have ( part 1 ; …, although…( sentence) ) although here is for the entire sentence, not special part.
@gregmat if you could ensure, is my understanding of your explanation is right please?