Server-side rendering matters because many AI crawlers and some search bots don't fully execute JavaScript the way a browser does — if your content only appears after client-side rendering, a crawler may see a blank or near-empty page and have nothing to index or cite. Server-side rendering, or static generation, sends fully-formed HTML on the first request, so the content is there regardless of whether the crawler runs scripts.
This is standard practice for any site chasing AI visibility now, not an edge case — Kando ships kandomarketing.com server-side rendered for exactly this reason, alongside llms.txt and JSON-LD.