The word "sustain" is found nowhere in the New Testament, and only a couple of times in the Old Testament, plus a few times in modern revelation.

In every usage other than modern revelation, the word has a contextual meaning that has nothing to do with the way it is used by Latter-day Saints today.

The idea of "sustaining" the prophets and apostles has no basis in ancient scripture other than anecdotal and analogical comparisons that constitute "a stretch".

"Sustaining" was clearly considered by Joseph Smith and the early Saints to be a form of "voting". The principle of "common consent" held that persons who served as leaders in the Church organization were not to do so without the "consent of the governed" - taken directly from the idea as it was contained in the Declaration of Independence.

At least, that is how it was in 1830. But soon the idea that the leaders of the Church had special entitlements and privileges crept into the minds of Joseph and others, and they began teaching that criticizing your leaders was sinful (see Bushman's biography of Joseph Smith).

Bottom line: The democratic spirit that was originally built into the Church was lost.