Blog on a subdomain, wondering why it doesn't lift the store

Blog on a subdomain, wondering why it doesn't lift the store
Client ran the shop on the root and the blog on blog.site.com. Two years of great content, zero benefit to product rankings. The authority sat on a separate entity that barely linked back.

What I did:
— moved the blog to /blog/ on the main domain
— 301'd every old subdomain post
— interlinked articles to relevant category and product pages

Subdomains are treated as somewhat separate sites for authority. Content in a subfolder feeds the same domain. For most affiliate and ecom plays, folder beats subdomain.

Caveat: a subdomain migration is a real move — full redirect map, GSC change of address, watch traffic for a month.