Ranks of the harbingers

How do you think they determine the ranking order of each one? And were any of the older harbingers displaced in rank, or was it pre set? I really want the game to tell us (or maybe I missed it) because all I can imagine is trial by combat for any new recruit.

Also, speaking of ranks, is Crucabena was the old fourth (you’d assume) what power could she possibly have had?

Edit: I know in game theyre ranked by strength. I phrased it poorly but i meant how does the tsarista or fatui determine the strength for the rank. For example; contest of strength or duels