Why is there a need for councils if the pope can just infallibly declare something. Also why are there votes for and against something by bishops, if bishops are lead by the Holy Spirit to vote right?
This is the principle of Collegiality. The Church is a living body. The head, together with its members is stronger than just the head. Popes have always consulted with fellow bishops and leaders of the church before making infallible statements. For example, when the dogma of the Immaculate Conception was proclaimed, the Church researched this belief by the study of the Fathers of the Church and other church documents left to us by the early church. The question was: Has this always and universally been believed by the Church? If there were objections, were they valid? After study and consultation, the Holy Father makes the belief Dogma–something that the entire church must hold and teach. Sometimes people think that the Pope is pushing his own agenda in these issues. The pope listens to the people who make up the Mystical Body of Christ. He listens to what the Holy Spirit is saying to people throughout the Church. The Holy Spirit confirms through him what the special needs of the Church is in that certain time. Look at the last 4 or 5 popes. See how the Spirit has moved through the Church.
Every bishop is a pontiff. Every diocese is a Church, called a local Church, which forms part of a larger Church. Twenty-three Churches form the universal Catholic Church. The Roman Catholic Church is the biggest of the 23, but not the only one. It is often referred to as the Latin Church, the Church of Rome or the Mother of all Churches. There is a problem with how these titles are understood today, but that’s better in the Eastern Catholic forum.
In any case, it’s not a matter of infallibility, it’s a matter of apostolic collegiality. The apostles themselves set the example by invoking the Council of Jerusalem, which we can read about in Acts. They understood that Peter could not rule alone. He was the bridge builder between pontiffs, hence the term “Supreme Pontiff”. He is the pontiff above all other pontiffs. But they are pontiffs nonetheless.
Each Church is autonomous. The pope cannot ride roughshod over them. This would be a violation of justice. Peter and his early successors did dictate to the other Churches without their input. Paul got a hearing that the Council of Jerusalem. Had Paul not gotten a hearing, every Gentile would have had to be circumcised and submitted to the Jewish laws that prepared for the coming Messiah. Those laws were no longer needed, as the Messiah had come. But were it not for a council, we would have been bound by Peter’s decision to require that every convert to Christianity embrace everything in Judaism.
The apostles understood the need for coordination, dialogue and feedback to Peter. Together, with Peter, they carryout the first council, the Council of Jerusalem.