Read more here: Order of Preachers – Dominican Province of St Joseph

“There is a legend that our Lady appeared to Saint Dominic to give him the Rosary, to teach him how to pray it and to commission him to propagate the devotion. This legend was circulated by Saint Louis-Marie Grignon de Montfort, the great Marian priest of the Dominican Third Order. The story is also mentioned in several papal encyclicals and in other authoritative sources, but it lacks historical evidence. It may indeed be true, but there is no documentation from the early 13th century to prove or disprove it. On the contrary, the meticulous depositions taken from eyewitnesses to investigate the life of Saint Dominic during his canonization process, although they mention many of his miracles and revelations, say nothing about the Rosary. Historical records, in fact, tell us a different story about the origin of the Rosary, saying that it developed in stages.”

My Two Cents Worth

Seems the Incredulous took over, after Vatican II, and started sewing the Sin of Doubt into Catholicism. If Papal Encyclicals, and Saints say Our Lady gave St Dominic the Rosary and told him to promote it, why sew doubts about that?

I do not think very much about folks who now call these ORAL & WRITTEN TRADITIONS “Myths!”

I think that is so wrong, to propose such nonsense.