He will go before him in the spirit and power of Elijah, 'to turn the hearts of the fathers to the children,' and the disobedient to the wisdom of the just; to make ready a people prepared for the Lord."
To make ready for the Lord a people prepared for him ...  This was indeed achieved, even though on a smaller scale than would have been desirable. Some of the apostles were first disciples of John.  (John 1:35ff).