I think that played a somewhat smaller role than Google seemingly gradually starting to take its position for granted and so everything became more focused on revenue generation and less focused on providing the highest quality experiences or results.

Beyond result quality it's absurd that it took LLMs to get meaningful natural language search. Google could have been working on that for many years, even if in a comparably simple manner, but seemingly never even bothered to try, even though that was always obviously going to be the next big step in search.