While Kagi does have a very specific audience in mind, I’m not convinced specialization vs generalization is a reason for a difference. Google also tailors ads for the audience, using information they have collected on you, people similar to you, as well as general time of day, current events, etc. It’s more that google wants you on their site for longer, Kagi wants you to find your result and move on, since the more you search the more it costs them.