Because the monopoly of Google is immense when it comes down to it.
Many upstarts, like DuckDuckGo, actually use Google and then display the results to the end user with them having no fear of being tracked by Google. In the same way Musk could use his own algorithms to decide what to display to the end user after scraping Google's results of the query.
Such search services are very vulnerable. My feeling is he has all the talent available to do it very quickly in a non-intensive way allowing Google to do all the heavy lifting.
DuckDuckGo had some partnerships with at least Yahoo in the past but I'm quite certain they now run their own crawlers and build their own search index. Brave Search is another really promising privacy oriented web search with an AI chatbot that they claim run on.
I don’t see how X could achieve anything better than what is already on the market just by scraping search results from other search engines. They must run their own web spiders and with the AI know-how they have they should be better equipped for running a search engine than the other web search providers were 10 years ago.