We tend to take the summary, abridged descriptions in the Book of Mormon at face value and, often, don't step back a bit and remember that what we have is presented as not even 1/100th of what could have been included - or that it was recorded by very few individuals from their own perspectives. We can accept them as prophets and good people without sacrificing our acknowledgment that they also were humans with personal biases and motives that influenced their writings - especially in the case of Mormon, who, like any historian with space and time constraints, had to pick and choose what to share and what to exclude.
For example, when I read the chapters about Mosiah's actions near the end of his life regarding the future governmental structure of his people, something jumps out at me that is easy to overlook:
1) Mosiah had taken leadership of a people more numerous than the Nephites. That simple fact opens all kinds of issues relative to his government-altering actions before he died.
2) If one of his sons wasn't going to take his place, there was a good chance that one of the people of Mulek who already was influential and popular would do so - especially if the kingship was determined by popular vote. Again, it is stated clearly in the text that the people of Mulek greatly outnumbered the descendants of Nephi in that area. In fact, the moment Mosiah's sons rejected the throne (and Alma the Younger also did), those other influential Mulekite contenders might have started agitating for the position very quickly.
3) Nehor is described as being another King Noah, in philosophy and intent. Amalici was one of his disciples. They are said to have gained a following FAR too quickly to have started a grass-roots campaign from scratch at the end of Mosiah's life.
4) If Mosiah knew either of them was likely to become the king, it would have provided the best possible motivation to change the system.
5) If you think about it, the best possible reason for Nehor, and then Amlici, to be extremely upset and demand what they had assumed they would attain would have been what they would have seen as an attempt to perpetuate the minority rule of the Nephites over them. Consider the situation in some Islamic countries even today; there are striking parallels.
6) It's easy to condemn Nehor and Amlici, given the descriptions we have of them, and I'm not trying to endorse them in any way - but it's harder to realize that they might have had a very compelling legal argument and an incredibly strong emotional appeal to a majority people ruled by those of the minority.
Many things are less clear than we tend to assume in hindsight - and many things in the Book of Mormon are pretty amazing when looked upon a bit more expansively than we tend to do.