You have given some helpful answers, especially as far as us regular mortals are concerned, but we have not yet hit upon the reason this was a great temptation for the Master.
To understand we must look through His eyes. This third temptation was carried over to the end of his ministry when in the Garden of Gethsemane He asked his Father to remove the cup from him so he would not have to be crucified, but when it was clear to Him this His personality wish was contrary to the Father's Will he acquiesced.
To understand this third temptation we must answer this question:
What was the greatest desire of the heart of Jesus that the third temptation seemed to fulfill and that the crucifixion seemed to frustrate?
Copyright 1999 by J.J. Dewey, All Rights Reserved