You can argue that correlation doesn't imply causation, but typically more contributors means more people who have played a part in the code and so more eyes on the project to catch issues as well as a higher bus factor and less key person risk.
And larger community means there's more rewards for a successful attack and therefore fewer latent security issues (ie, obvious ones are more likely to be caught).
I think companies considering building in-house packages are just trading one risk for another. Especially with LLMs, it's going to be a lot easier to find vulnerabilities in your internal dependency than it would be in a battle hardened dependency used by 100s of others.
And larger community means there's more rewards for a successful attack and therefore fewer latent security issues (ie, obvious ones are more likely to be caught).
I think companies considering building in-house packages are just trading one risk for another. Especially with LLMs, it's going to be a lot easier to find vulnerabilities in your internal dependency than it would be in a battle hardened dependency used by 100s of others.