The parent library in that situation was a popular library with a whole team of contributors who could reject malicious PRs. But a PR that just updates every dependency (including a malicious update to the tiny library) can easily go unnoticed.

And that was one situation. The mindset of the Javascript ecosystem is still to maximize code reuse, meaning even if the tiny library maintainer isn't a maintainer of the parent library, the parent library still frequently clings to their one-line dependencies when I've tried removing them. Thus granting the tiny library owner tons of power like the maintainer of "colors".