This was very likely part of a much larger study, but they had the data to test these hypotheses, so they did. Happens all the time in the social science. You have TONS of data from a big study, so you think about the hypotheses that you could test with the data set you have, so you do that and write up the results to be published.

I find that 99% of people who question scientific funding have literally no idea how any of it works. But that’s people for you.