Sant looks like saint and is not related to it. The English word descends from Latin sanctus, meaning consecrated or holy; the Indian word comes from the Sanskrit sat, that which is true or real, so a sant is one who has to do with the real. The collision is a coincidence of sound that has misled generations of translation, and it matters because the two categories are built differently. A saint in the Latin sense is recognised after death by an authority. A sant is identified in life by what he teaches and by the verses that carry the teaching, and no institution confers the description.
The tradition the word names took shape in North India from roughly the fourteenth century and is usually described as nirguna bhakti, devotion to a God without attributes or form. That commitment carries several consequences at once. If God has no form there is nothing to install in a temple, so image worship falls away. If God is reached directly there is no necessary intermediary, so the ritual authority of the priesthood falls away with it. And if the teaching is to reach the people who need it, it is composed in the language they speak, so the poetry is in Hindi dialects, in Punjabi, in Marathi and in Gujarati rather than in Sanskrit.
The social composition follows from that. Kabir was a weaver, Ravidas a leatherworker of a caste treated as untouchable, Namdev a calico printer. Sanskrit learning was closed to them and they wrote anyway.