After Christ was crucified and the Apostles killed, the spread of unclear and false doctrines spread slowly but surely throughout the Church that Christ had established. With the Apostles gone and the Priesthood Authority that Christ had given them no longer on the earth, the world was stuck in a time of spiritual famine.
"Behold, the days come, saith the Lord God, that I will send a famine in the land, not a famine of bread, nor a thirst for water, but of hearing the words of the Lord: And they shall wander from sea to sea, and from the north even to the east, they shall run to and fro to seek the word of the Lord, and shall not find it."
We see that after the passing of the Apostles the "One Lord, one faith, one baptism" (Ephesians 4:5) which Christ established descended into that time prophesied. As the world moved on and those trying to follow Christ were persecuted and eventually assimilated with the basic population, the confusion that comes without revelation at the head of the church was answered by a council of men who decided what was and what wasn't true. While these men were undoubtedly intelligent and well meaning, they lacked the first and basic step to receiving inspiration. Asking Questions. And by so doing stopped the population at large from asking questions of Heaven. Once the questions stopped, so did the answers.
The Lord hears and answers questions. This I know. In 1820 there was a young boy who had questions. He wanted to know what church he should join but kept getting different answers from those surrounding him. He decided to turn to his Bible to find the answers he sought, when he found
"If any of you lack wisdom, let him ask of God, that giveth to all men liberally, and upbraideth not; and it shall be given him."
He knelt in a grove of trees near his home and prayed to know what church he should join. When he leaned essentially what I just told you above. God and his Son, came to the young boy and called him to be the instrument through which They would restore Christ's church to the Earth. It would be "built upon the foundation of the apostles and prophets, Jesus Christ himself being the chief corner stone" (Ephesians 2:20). I know that since that time, we have had an authorized servant of the Lord leading the Church by inspiration and revelation from God. I know that the Lord lives and that His church is again on the Earth. In the name of Jesus Christ. Amen.
Here is the story of the Restoration.