What they did
Ahrefs set the number of referring domains for each page against its estimated organic traffic across the same 14 billion page index, then looked at how traffic changed as link counts grew.
What they found
Among about 20 million pages with zero referring domains, only 2,997 managed more than 1,000 monthly search visits. Across the index, more referring domains lined up with more traffic.
How much weight to give it
Ahrefs itself writes that correlation does not imply causation. Good pages tend to attract both links and traffic, so links may be a symptom of quality rather than the cause of the traffic. The safest reading is that competitive queries usually need links, while low-competition topics often do not.
What it doesn't prove
Traffic is estimated, and the link and traffic figures come from the same crawl, so both share any index bias. The finding says linked pages tend to get traffic, not that a given new link will deliver a given lift.