The only thing I am clear about this query is the need to avoid a literal translation. I believe it is better to use a verb such as “profundizar”, “investigar” or even “analizar”. My problem in this context is precisely the lack of context, i.e. that I do not know what “insight” means exactly here. However, this would be my translation suggestion:

English source:
If you scratch below the surface of even the most legendary moments of insight, you'll always find a history of collaboration.

Possible translation:
Si profundiza(s) en los instantes incluso más conocidos del entendimiento/de la comprensión, siempre encontrará(s) una historia de colaboración.



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Note added at 1 hr (2021-11-23 21:13:25 GMT)
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I found this reference confirming the metaphorical meaning of the expression:
https://english.stackexchange.com/questions/10671/what-does-...
What does "scratch below the surface" mean?
3
Scratching the surface is related to scratching below the surface. When you scratch the surface of something in the NON-LITERAL SENSE, you're just beginning to learn about something and only know a few superficial details. When you scratch below the surface, you've learned more information about a subject. At that point, you have moved beyond a simple understanding of the subject and are delving into the depths of it, to use another idiom.
Both scratching below the surface and delving into the depths are similar in their idiomatic meaning in that they both imply that you are learning more about a subject.
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"scratch below the surface" would mean to definitely go deeply into something.