Tradition or Belief?

In Chinua Achebe's novel things fall apart, the village at the core of the book is heavily religious just like all of the 8 other villages surrounding it. There's a part of the book where the entire village goes to the playground to watch people's trials where they must ask their ancestral spirits who's right, who's wrong, or what they should to fix the problem. There are 9 ancestral 'spirits' that come and sit, ready to judge people. I'm curious right now whether the village people truly believe that these are spirits, or if they simply hold it as a custom for the men of their justice system to dress themselves and play the role of an ancestral spirit. IT says clearly in the book. Chinua Achebe describes the spirits' arrival as a terrifying spectacle, but later goes on to mention how people had recognized akonkwo in the crowd but kept it to themselves. "Okonkwo's wives, and perhaps other women as well, might have noticed that the second egwugwu had the springy walk of Okonkwo. And they might also have noticed that Okonkwo was not among the titled men and elders who sat behind the row of egwugwu. But if they thought these things they kept them within themselves." So now I'm left wondering what it is that the people actually believe. It seems taboo to speak against the religion, yet it seems impossible for them to beliieve that the people holding the trials are truly spirits.