Systemic nepotism is not reason to avoid investigating a specific incidents where it is especially prevalent.

There's also a difference between hiring someone you know vs. only hiring a person because you know them.

Besides which it is possible to have hiring practices that make this abuse more difficult: where I work friends & family of a candidate are obligated to identify such prior relationships during the hiring process so that another person can review any decision to hire that candidate.

Maybe things are that bad at Google, but that would be precisely the reason for casting more light on the issue in order to change things.