The internet needs search engines. Search engines spawn SEO. SEO enshittifies search. I honestly don't see how it could have happened any differently even if all the players were different. Search was essentially a solved problem by 2000, and everything since then had been an arms race between search engines and SEO. I'm surprised search engines have remained as useful as they have for as long as they have.

Monetization through ads certainly adds to the incentive to practice SEO, but even without it, people put up web sites because they want visitors, so they were always gonna have an incentive to game whatever search algorithms are most widely used.

The only way I know of for things to have happened differently would be the same mechanism that prevents traditional media and stores from being total crap-fests: having a higher barrier to enter and stay in the market, so participants who don't find a somewhat loyal customer base are forced out.