Google Trends is a good way of gauging interest in a subject.
Substantiate this statement, ideally keeping in mind that it's been made and refuted multiple times before, and the real correlation with Google Trends has already been documented. (i.e. please provide a new argument which sufficiently overturns the understood cause, and don't waste our time with the ones already dealt with)
I don't understand your question but there's a strong correlation between general interest in a subject and Google Trends results.
It is not a perfect but it tracks public interest in a subject in ways that we expect it to. For example, Trends for Donald Trump predictably blow up in a way that's consistent with his political career.
https://trends.google.com/trends/explore?date=all&geo=US&q=Donald%20Trump Not remarkable until June 2015 when he started his run for President. By contrast, here's Hillary Clinton (
https://trends.google.com/trends/explore?date=all&geo=US&q=Hillary%20Clinton) which also shows an expected result. Interest spike during her run for President but dies down shortly afterwards, because she isn't the President.
Google Trends even shows predictable seasonal changes in interest, for example, here's Hayfever (
https://trends.google.com/trends/explore?date=all&geo=US&q=hayfever) and predictably the search interest rises in the summer months, decreases in the winter months, quite consistently year over year. Conversely, here's results for Influenza (
https://trends.google.com/trends/explore?date=all&geo=US&q=influenza) which likewise spike each winter season, and die down in the summer months, which is consistent with the flu's seasonal pattern.
This should be solid enough evidence to support the notion that Google Trends is a good indicator of general public interest of relevancy in some thing. Therefore, my earlier statement that Flat Earth has seen a marked change in search interest since 2015 is solid, and Google search interest demonstrably correlates with general interest in a subject.