It solves a problem that was puzzlimg mathematicians for millennia - I wouldn't call that a footnote. You may not consider pure math applications interesting, but that doesn't make them unimportant.
Galois theory is big today because it provides a connection between a ring theory and field theory. This has huge applications for other branches of modern math - for example, number theory. But that always culminates in a pure math application, which makes it a footnote, I guess.
It makes it into a silly little footnote, a very little footnote, I was both sad and disappointed when I read and understood it in an appendix.
Now back to Pi + e = Pie.