I don't think parent post is claiming that Google is using other people's networks to scrape the web only that they have a strong incentive to keep other players from doing that.

No, there are other scrapers that Google doesn't block or interact with. You can even run scraping from GCP. This has nothing to do with "only Google is allowed to scrape". They even host apps which exist for scraping data, like https://play.google.com/store/apps/details?id=com.sociallead...