Heading structure affects featured snippets because a clean hierarchy lets Google locate and lift a self-contained answer block that sits directly under a relevant heading. The snippet engine is not reading your page as one long blur of text; it is looking for a tight, complete answer it can pull out and display on its own. Headings are the map that tells it where those answers live. When the structure is clear, the right block is easy to find and extract; when it is muddled, the answer may be there but harder to isolate.
The mechanism comes down to extractability. A featured snippet has to make sense out of context, stripped from the rest of the page and shown above the results. For that to work, the answer needs to be a discrete chunk, and a heading is what signals where that chunk begins. A heading that names the question or topic, followed immediately by a concise, complete answer, gives Google a clean unit it can confidently lift. Without that framing, a strong answer can stay buried inside a paragraph that does not stand alone.
This is why the heading and the content under it work as a pair, not separately. The heading earns the snippet by labeling what follows, and the content earns it by actually being self-contained and concise enough to display. A clear heading over a rambling, multi-idea section still will not produce a clean extraction, because there is no tidy block to lift. The structure enables the snippet only when the block beneath the heading delivers.
Hierarchy matters for the same reason at the page level. A logical order of headings and subheadings helps Google understand which sections answer which sub-questions, so it can match a query to the precise block rather than guessing. The structure is doing the work of pointing the extractor at the answer most relevant to the search.
When you write for snippets, put a clear, descriptive heading directly above a concise answer that stands on its own without the surrounding text, then let the supporting detail follow. That pairing is what turns a good answer into an extractable one.