I use Notion for all my notes, so it didn't make sense to download them into an md file, figure out the logistics, and push/pull with other SSGs like Quartro, Eleventy, Hugo, or Jekyll. I could have used another CMS, but since I already use Notion, it's easier to keep everything in one place. Notion also offers unique features that other CMS don't: WYSIWYG for various components, block-level permissions (to add drafts to post text), easy collaboration, and more.
There are some NextJS options that somewhat meet these criteria, but since I'm not familiar with NextJS and didn't want to learn it at the moment, I didn't explore them. Most of them also relied on publicly shared pages. Astro, on the other hand, provided everything I needed.