dawnstar - 10:19 am on Sep 26, 2013 (gmt 0)
Who knows? Google be CRAZY!
If I try to think like them, maybe they see your homepage as being sneakily on topic and helpful for your target audience and think:
Ah...Ha! You're trying to game our system with your helpfully relevant website! We'll teach you sonny, by ranking a totally off topic page from said website, so you'll know that we know about your helpful homepage but we ain't ranking it.
Sorry for the Sarcasm, but if you find a way to sort it please share for the rest of us wrestling with the Google Black Box.