For those who have 'discovered' the Jesus of the Bible, resurrected from the dead and alive today, they swiftly spot that the Jesus of Joseph Smith is not the same Jesus. He is claimed to be the first spirit-baby born to the god Elohim and his wife in some other universe. They named him Jehovah and later, his plan of salvation was superior to his brother, Lucifer's, so this Jehovah became born as a baby on earth to carry it out. No Bible-believing Christian can accept any of that, which is why the testimonies of those witnesses to the golden plates are discounted. But there are more reasons for discounting them than that.
An interesting thing about the Book of Mormon (BofM), which claims Jesus visited the Americas centuries ago to establish the start of a religion that would lead to the religion Joseph Smith proposed in the early 1800s, is that this 19th century religion is dependent on the truth of the claim that the initial BofM was completed 1190 years before the King James Bible, from which the BofM quotes extensively (though not entirely accurately). Is that not suspicious? We also have to believe that Joseph Smith was given golden plates in the early 1800s. They had been laid in a stone chest at the beginning of the 5th century, and contained "the fulness of the everlasting gospel." These plates were apparently written in "Reformed Egyptian" characters, and needed to be translated into English (by Smith who had to wait 4 years before getting angelic permission to start that work). Thus came into being the English BofM, testified to as authentic by various witnesses. Let's check them out.
I have in front of me photo-copies of the "Testimony of Three Witnesses" 1830 original edition, and of the "Testimony of Eight Witnesses" 1830 original edition. The three were, Oliver Cowdery, David Whitmer and Martin Harris. Despite saying that they saw the plates and testified that the translation of them was "by the gift and power of God", later on thousands of changes had been made to the once-only translated text, thus invalidating their testimony. Further, all three of them later apostatized from the Mormon church. Joseph Smith accused Cowdery of having printed counterfeit money, and a denunciation of all three is found in the Mormon book, Doctrine and Covenants, page 232.
The eight witnesses were Christian Whitmer, Jacob Whitmer, Peter Whitmer Jnr., John Whitmer, Hiram Page, Joseph Smith Senior, Hyrum Smith and Samuel H. Smith. The original edition of their testimony calls "Joseph Smith Jr. the Author and Proprietor of this work" but later editions drop the "Author and Proprietor" claim, putting instead, "Joseph Smith Jr., the translator of this work." That invalidates the original testimony. Further, five of the eight later apostatized from the Mormon church.
Finally, consider evidence for where the BofM really came from. Around 1810 there was a Congregational preacher called Solomon Spaulding. He was an avid reader with a great interest in Indian folklore and archaeology. He had a master's degree and was totally familiar with the King James Bible. In his own handwriting he produced a book he called Manuscript Found. There is reason to believe this book was stolen from Patterson's Print Shop, Pittsburg. One reason is that, years later, some original, hand-written pages of the BofM were lost at the printers, at its first publication. Smith went home and came back with the missing pages, in long-hand writing. These pages are in Spaulding's own handwriting, but he was dead when the BofM was supposedly translated.
Eight people who read both Manuscript Found and The Book of Mormon have testified under oath that they are both the same. They were, John Spaulding, Martha Spaulding, John Miller, Henry Lake, Artemas Cunningham, Aaron Wright, Nahum Howard and Matilda (nee Spaulding) Davidson (Solomon Spaulding's widow).
I suggest that if you want to consider the testimony of eight people, you go by the ones who knew that Manuscript Found predated the later printed title The Book of Mormon.
Sources: The Book of Mormon - True or False? by Arthur Budvarson, pp25-28, 1959.
The Facts of Mormonism are Stranger than Fiction, p13, Eric Clarke, 1986