An interview with some Blizzard people about how they designed the collab and also why they chose G.I.Joe in the first place.

https://comicbook.com/gaming/news/overwatch-2-new-gi-joe-collab-interview-june-2025/

Apparently, their art director is a Joe fan and they simply thought it would be a good fit for the game even if it's not a mega popular thing.