A quarter of the websites on the internet are behind Cloudlfare/Akamai with anti-scraping enabled. Of course they want to end up on Google, so Google/Bing get a green light from Cloudflare.
IMHO, that basically makes it impossible for anybody else to spin up an index and compete with Google Search. They cannot just scrape, they also have to work around anti-scraping measure by these CDNs. They have to maintain these workarounds, while trying to scrape as much as google has scraped so far, which is already a feat in itself.
Once you have this, you have everything: a critical mass of users, ads, data set for AI, ...
I dare anybody to scrape Reddit or Stackoverflow from scratch today.