If lightning hits a dead tree, it will still travel down the tree to the ground (on the outside of the trunk), but it likely won't make the tree explode because of an inadequate level of sap in it.
The reason trees explode when struck by lightning, is because the sap is superheated to steam instantaneously.
The normal level of volatile eucalyptus oil naturally in the air, is at too low a level to be ignited by lightning. However, in a fire, heated trees close to the fire front can release large amounts of volatile oils that further exacerbates the fire strength. There is a known feature of bushfires, termed "a crown fire".
A crown fire occurs in front of the main fire front, and is driven by strong winds, which send the fire front through the treetops, aided by the high level of volatile oils at the treetop level.