A quote from the site of the Roman Catholic TV Télé Lumière:
The Rosary probably began as a practice by the laity to imitate the monastic Divine Office (Breviary or Liturgy of the Hours), during the course of which the monks daily prayed the 150 Psalms. The laity, many of whom could not read, substituted 50, or even 150, Ave Marias (Hail Marys) for the Psalms.
So the Rosary came to replace the Word of God. Instead of the Psalms, i.e. prayers addressed to God, they preferred to worship a human…
Grace be with you!
Disciple of Jesus Christ