“Topical authority” is not a Google term. It’s industry shorthand for three things working together: breadth of coverage, depth/quality of content, and a sane internal link structure that helps both users and crawlers understand the site. Google’s public docs don’t say “build topical authority,” but they do say their systems reward helpful, reliable, people-first content, use many ranking signals, and use links both for discovery and as a relevance signal.
A site with strong topical coverage but no off-site trust can absolutely rank for long-tail and lower-competition queries. That is especially true when the content is tightly organized, answers real questions, and has good internal linking. Google also explicitly says its systems analyze site link structure for things like sitelinks, which reinforces that internal architecture matters.