A point to consider is what "a trillion dollar business" actually means. The math of markets forces income to match how hard it is for someone else to do some work. Take the food situation like food. Feeding someone is critical to their very existence, but cooking is such a generic skill that the margins on any restaurant get squeezed down to not so much. So even though the value of feeding someone is very high, the value add that a business can lay claim to is very low adn they don't make much money.

The threat here isn't that someone will do better than Google as much as a proliferation of cheap AI might trash the "trillion" part and replace it with "billions". If someone could cheaply bundle a search engine with a web browser or OS then Google Search is vulnerable. I mean, what if an AI model could be made small enough to work offline? How does Google make money?