Is it a red flag if the justification for my research (why it is likely to matter) is popularly sourced?
Research need not be completely inward looking: a snake eating its own tail. All applied research, in fact, is rooted in real world concerns. The fact that the questions have been little studied in the past is not a reason to avoid them in the future. 

In fact, "its interesting" is enough of a justification for a lot of research, whether theoretical or applied. 

And having a potential application immediately may make it more interesting, actually.