Second, the search engines that used to help drive users to Reddit mostly all have AI summaries / AI answers right there on the main search page these days. A lot of people read those AI results, get what they want right from Google (or otherwise), and never click any links over to Reddit.

Not just that but iirc a decision by reddit causes certain threads to only be displayed in search results without a post title and a description saying "the website doesn't allow us to show you content" so why would anyone click on the Reddit links in a sea of other links?