First, schools with smaller stadiums played more home games in 2014 than in previous years, so the average across all games decreased. If you normalized to assume every school played the same number of games, then average attendance increased by about 1%.
Second, more marquee games have been played at neutral site games in recent years, which are not included in the totals. Almost all neutral site games will have a larger attendance than the average.
Just looking at NDs numbers, since 2006, our number of home games have been 7,7,6,7,6,6,6,6,6. Even thought we have (technically) sold out every game, the national numbers will decrease slightly in the years we play 6 instead of 7. Now perform that exercise for every major program, and I am confident you will find 2014 had the lowest number of home games among the last decade.
I pointed out these issues in the original thread, but people just wanted to talk about how kids these days would rather spend their Saturdays on facebook.