Sociological: Alma and Amulek are brought to the scene of the terrible torture. There are a couple of important points that may be derived from this statement. The first is the rather obvious fact that Alma and Amulek were viewing from the outside rather than the inside of the conflagration. If Alma and Amulek caused this problem for the chief judge, and it was Alma and Amulek were brought before him and accused by the people, how is it that they escaped punishment and others were put to death?
Once again we return to the concept of human sacrifice. The sacrifice of the others would bring appeasement from the deity who would be supposed to desire such a sacrifice. Secondly, at least Alma is a rather important man from Zarahemla. While he is not the sitting chief judge of the entire polity, he is the immediate past chief judge. It is very probable that the Ammonihahite judge would be loathe to harm Alma fearing some retaliation from Zarahemla. Amulek would be under the protection of Alma as a companion.
It is also a part of the Mesoamerican concept of human sacrifice that well known captured enemies were kept alive and "on display" for a number of years (Schele, Linda and David Freidel. A Forest of Kings. William Morrow and Company, 1990, pp. 190, 193-4, 464). Thus Alma and Amulek may have been important enough to warrant ceremonial detainment rather than a more immediate death.
The second point that we may derive from this brief description is that the burning occurred in a place that provided the ability to bring Alma and Amulek to witness it. Again this may appear to be a simplistic point, but the importance is in the probable public nature of this martyrdom. It is likely that all of the population of Ammonihah would have been at least theoretically capable of watching the martyrdom. This again is consistent with the concept of human sacrifice, with was a very public performance in Mesoamerica.