Only one of two outcomes is possible. He either told the truth or it is a lie. Let's look at some of the possibilities.
Joseph Smith was 14 years old when he first declared that he had an experience beyond his an what most of us would expect as an answer to an honest inquiry through prayer. While many have declared visions regarding deity, his was different.
When he declared that he had seen God the Father and Christ he was immediately persecuted. His story was a complete reversal of orthodox theology. He said God was corporeal and the mainstream sectarians and Catholics had long declared God to be a mysterious incorporeal substance.
From that time on he was called a liar and other things. Because he would not back down from his declaration other methods were incorporated to try and get his message stopped. He continued to add additional stories of visions and messengers from God. In every case following Biblical patterns and theology. Why was his message so different and contradict the longstanding traditions of religious professors?