The point is that majoritarian decisions have nothing to do with it either way. The Chruch has the promise of Christ that the gates of hell shall not prevail over it. There is also a promise to St. Peter from Christ, that He will protect Peter personally from error. Based on that, the Chruch believes that however her decisions are reached, by consensus, majority, or papal infallibility in absence of consensus, she is protected from error by the Holy Spirit. It is not a belief akin to what one might have about the American justice system, for example, that because of its juruducal constitutional structure, it is self correcting. It is a mystical belief in the promise of Christ.
But I thought that the structure was set up so that you would know something is correct and protected if there was a consensus. (I have no idea how often the Pope has decreed without a consensus.) I don't see how it is different from a normal democratic system in terms of the "business" of the Church. I thought that protection was identified by consensus.