Google came along when the search industry was in its infancy, with multiple providers vying from top-spot. We have now had over 20 years of dominance, refinements to get it to what it is today. Entering the market today is on a whole different spectrum to what it was back then.
When Google search came, they started their search engine by providing a clean search page with no ads, at a time when all the others had cluttered, ad-filled, shitty pages.
Users picked Google because it was the better experience back then. Today, if a search engine comes along that gives you great search results and privacy, it will become very popular quickly, because a lot of us are fed up with Google and want them to go away completely.