The cycle of wickedness and destruction often includes a complete inability of the wicked to detect their grave errors. They have their religion, and are comfortable with it. They think their pretenses are enough.
Ezekiel saw a vision of the destruction of the "chosen people" beginning at their Temple. The destroyers were told to wait before the slaughter began. First an angel would mark the foreheads of those who "sigh and cry for all the abominations that be done in the midst thereof." (Eze. 9: 4.) Meaning there were a few among the chosen, who knew their religious practices were used to justify abominable behavior. These few did not just condemn the wicked, they "sighed" and "cried" for their fellow saints. They prayed, made intercession, hoped for more time, and urged repentance.
The larger group, however, were content with their abominations and thought themselves righteous. They were not marked, nor spared. The command was given to slay them all, utterly, and spare none "both maids and little children, and women." (Eze. 9: 6.)
In the vision Ezekiel saw the destruction begin at the Temple. (Eze. 9: 6.) It began there because it was the Temple which these corrupt people believed to be proof of their great righteousness and also their favor with God. Therefore the destruction needed to begin there.
The angel faithfully marked only those who were aware of the abominations and who would not join in with it. (Eze. 9: 11.) When the destruction began, the Lord was committed to His judgment, and declared "mine eye shall not spare, neither will I have pity, but I will recompense their way upon their head." (Eze. 9: 10.)
This is a useful chapter to consider. (Ezekiel Chapter 9.) It reinforces the importance of repentance, when it is offered. When the offering ends, it is followed by judgment and destruction.
How odd it is that the self-proclaimed "righteous" are almost without exception those who are most wicked, fallen, abominable and proud. You rarely encounter a corrupt group in the Book of Mormon who are not also quite involved in a false religion. The false religions in the Book of Mormon frequently teach that the followers are righteous and highly favored of God. (See, e.g., Alma 31: 14-18.)
Wouldn't it be amazing if this kind of mistake could be made again by people who think themselves holy, better than others who do not enjoy the fullness of God's favor/Gospel, and destined for salvation while all others were doomed to an inferior kingdom? It's almost too ridiculous to even consider. Those things are behind us now, aren't they? Because we are promised salvation, and for us to fail would be for God to fail, and we know He's not going to do that.