And why did they ignore Yahoo?
Yahoo was probably the web's original search engine. Except it wasn't. It started out as an attempt to categorize the web, librarian card-catalog style, an approach doomed to failure.
Even before Google, it was obvious that search, the more AI the better, not classification, was the way to go. It was obvious that whoever did best at search would win.
Of course, Yahoo abandoned the librarian approach fairly early, but not before real search engines took the lead.
Google's timing was fortunate. It was able to snap up talent laid off by the likes of Yahoo in the 2000 bubble bursting.