I think it depends on the interests of the membership at any given point. For example, during U.S. election years, political threads tend to get a lot of views compared to most other subjects. At the moment, threads about COVID seem to be a hot topic. So it largely depends on larger trends beyond the scope of RF as well as the interests of most active members.
This is merely an educated guess, but as far as thread view count goes (including from guests and lurkers, not just active members), I suspect certain keywords may play a role depending, again, on ongoing trends. For instance, if a member started a thread with "COVID," "Biden," "existence of God," etc., in the title nowadays, it could get more search-engine hits than, say, a thread with a relatively rare phrase such as, say, "epistemological rhetoric" or "demagogic propaganda" in the title.