Wisdom rather than strength is what the fifth line contributes. Legge's translation describes the advance of wisdom, such as befits a great ruler, and promises good fortune, while the Little Symbolism explains it as the way of pursuing the due mean. In a hexagram built on two strong lines rising into four yielding ones, the ruling position is held by softness, and the text names discernment, not power, as the quality that justifies it.
A yielding stroke occupies the fifth, odd place, incorrect by the letter of the standard rule, yet central in the upper trigram Kun and holding the seat of authority. That combination is the line's whole argument. A ruler of this kind cannot outmatch the strong lines approaching from below and does not attempt to, governing instead by judging correctly who is drawing near and on what terms, which is what the second line's partial independence already implied.
Set against the fourth line, praised only for occupying its place properly, the fifth is praised for the use it makes of a place that does not properly fit it. The due mean the commentary names is the balance between receiving every approach and refusing them all, and holding that balance is what this hexagram treats as the whole art of governing an advance.