When copying the printer’s manuscript from the original manuscript, Oliver Cowdery accidentally replaced dethroning with destroying, perhaps because of the occurrence of destroying within the same line of 𝓞. In addition, there is the visual similarity between dethroning and destroying (as well as the semantic compatibility in this instance) that would have facilitated the copying error.
To be sure, dethrone and destroy are not synonymous, yet in many passages either word would work. For example, we have six other occurrences in the text where a ruler (a king or a judge) is “dethroned”; and except for the example in Alma 51:5, the verb destroy would also work in place of dethrone:
On the other hand, there are at least two clear cases where a ruler (a governor or a king) is “destroyed”; in these two cases, destroy could be replaced by dethrone:
With respect to the last example, note that we have a single passage where both destroy and dethrone are used to refer to the same act:
Since either dethrone or destroy is possible in Alma 24:20, we let the earliest textual sources determine the reading.
Summary: Restore the original occurrence of the verb dethrone in Alma 24:20: “for the purpose of dethroning the king”.