Keyword research usually starts with volume, which is the easiest number to obtain and the least predictive of outcome. What determines whether a page can rank is the intent behind the query.
Search engines rank against a resolved intent
For any given query, the results already reflect a judgment about what people who type it actually want, inferred from what they click and where they stay.
A page offering a different kind of answer competes against that judgment rather than against the other pages, which is a much harder position.
The existing results are therefore the clearest available statement of what a page has to be in order to rank at all.
The same words serve different needs
A query can be informational, comparative or transactional, and the wording often gives no indication of which.
Someone searching a product category may want to understand what it is, compare options, or buy immediately, and the engine picks whichever dominates.
Where the dominant intent is informational, a product page will not rank regardless of its quality, because it answers a question nobody asked.
Volume is often attached to the wrong intent
The highest-volume queries in most categories are broad and informational, which makes them expensive to win and poor at producing revenue.
Lower-volume queries closer to a purchase decision convert at rates high enough to outweigh the traffic difference by a wide margin.
A ranking on a broad term also attracts visitors with no purchase intent, which raises hosting and support load without contributing anything.
Reading the results is the research
Examining what currently ranks tells you the format expected, the depth required, and whether the engine favours retailers, publishers or manufacturers for that query.
Where the first page is entirely comparison content, a brand page will not displace it by being better written.
The result set also shows which features occupy space, since a page dominated by other elements leaves far less traffic for the ranked results below.
Intent moves and results follow
What people mean by a query changes as a category matures, and the results change with it, sometimes reordering entirely.
A page that ranked for years can lose position without any change to itself, because the intent it served is no longer the dominant one.
Periodically re-reading the results for the queries that matter is therefore a maintenance task rather than a one-off piece of research.