I think that slicing the universe of tech/startup companies into categories like 'successful' and 'not successful' and then creating some kind of causal story a

I think that slicing the universe of tech/startup companies into categories like 'successful' and 'not successful' and then creating some kind of causal story about how, maybe, 'the company in question uses a monorepo as part of their infrastructure mythology' is ultimately flawed, and puts way too much emphasis on historical artifacts that may have some bearing on the overall success of an engineering organization and its culture, but that are really just incidental to the truly key elements that defines an organization's success. I'm sure that Facebook's success lies not really in it using a monorepo, but the fact that it had a very pure hacker mentality, trying new things out, going with what worked, and making large strides in real tech and not trying to come up with complexity until there was a good reason to. If anything, I could see the opposite being true. It is so easy to properly do dependency injection and split things into services that there is no real reason to have a monorepo these days.