Complex sentence: According to Beesley, many have written that interest in the Deseret alphabet died with Brigham Young; but this isn't true, it was already regarded as a failure during Young's time.
Split into simpler sentences: According to Beesley, many have written that interest in the Deseret alphabet died with Brigham Young. This, however, isn't true; the alphabet was already regarded as a failure during Young's time.