“… To bestow reward upon the righteous who sustain the world that was created by ten utterances.”
We know that the world exists in the merit of thirty-six tzaddikim who exist in each generation. When one is niftar, another tzaddik takes his place.
However, it is reasonable to believe that an individual does not become a tzaddik overnight and he was already living before the previous tzaddik was niftar. If this is so, then there are more than 36 tzaddikim extant at any given time in the world.
R’ Volf of Sidrikov answered this question very simply. The fact is that every generation is on a lower madreigoh spiritually than the preceding one. Accordingly, the tzaddikim, too, in subsequent generations are not on the same elevated madreigoh as their predecessors. Consequently, at the moment when a tzaddik leaves the world, a “Lamed Vov’nik” appears to replace him, but it is someone who could not have been a tzaddik at the same time as the one who predeceased him.
chazon Ish
the Chazon Ish once said that his influence of Torah is through his gentle way of speaking when he is teaching!