Evolution

I was listening to an old recording of Maybelle Carter singing "Wildwood Flower," the other day, and she sang, "I woke from my dream and all idols was clay." What interests me was not the subject/verb agreement (this is Bluegrass, after all), but the "idols was clay." This is an evolution in language.
The original passage is from the Old Testament, and relates to a vision of a statue, and idol, with golden head, silver shoulders, and so on down the torso, until the feet, which were of clay. The vision typifies the "golden age" hypothesis, which states that things were better back then, and got worse as we neared the present, where things are miserable.
The meaning of the idol shifted somewhat through history, coming to mean, in the 20th century, that an idol had "feet of clay," meaning that an admired person had a serious flaw.
As Mother Maybelle sings it, the meaning has shifted again. Now it means that anything which we thought was good has gone bad.
This is the way language works. The shift is not good, not bad, just there.