Couldn’t they just show ads alongside the search result?

I am sure they can figure out even better. Like put the product purchase link in the answer.

For sure, but is that proven to be as good at revenue as the status quo?

It’s kind of like how the movie industry killed their Blu-ray, DVD, and theater ticket sales in favor of streaming.

Or how digital download/streaming music took decades to match the pre-Napster revenue peak of the industry. It’s still barely ahead of that level and that’s before adjusting for inflation.