It actually predates Christ. The 150 Psalms have been prayed by Levitical Priests since the Time of King David. After the time of Christ - The Priests of the Catholic Church continue this practise in the Office they must pray daily. ( not all 150 every day but over a period of time they pray all 150)
The Psalter came about because of a lack of Bibles and or access to the Psalms - Devout orders wishing to offer the Psalms to GOD - substituted The Our Father for Each Psalm and that was known as the Psalter.
The Marian Psalter , of course being 1 Hail Mary for each Psalm.
St Dominic was already aware of the Marian Psalter at the time of his vision. And it is the Blessed Virgin Mary herself that requested the Marian Psalter. So Devotion to the Daily Holy Rosary began with St Dominic - rather than to say it was invented by him. And of course - many other Catholics throughout History have recommended the devotion. Pope Leo the XIII wrote 13 encyclicals on Devotion to it.
Pax
Which brings us back to: which Dominic?
Blessed Alanus claimed the devotion began with the founder of his order two centuries after the latter died - a view that did become popular in later ages due to the efforts of other Dominicans who were also devoted to the Rosary. Historically, however, whether this is the case is unclear and rather doubtful, since no contemporary source makes any explicit connection with Domingo de Guzmán and the Marian Psalter: there is a
total silence in the records, biographies, hagiographies, and even the iconography of St. Dominic before Alanus de Rupe.
That being said, as I’ve mentioned, it seems to be more likely that a Carthusian named Dominic of Prussia was the originator of the practice of meditating on at least fifty moments on Our Lord’s and Our Lady’s lives while reciting 50 Hail Marys, with clauses referencing the event being meditated on sandwiched within the prayer (“
blessed is the fruit of thy womb, Jesus, whose birth was announced by the angel…”) Now, Alanus was publically a critic of the Carthusian Dominic and his increasingly-popular devotion: he didn’t like the idea of meditating on just fifty events - he believed that it should retain the number of 150 - and he also disliked the name
rosarium for the prayer: his preferred named for the rosary prayer was the “
New Psalter of the Virgin,” highlighting thus that the rosary had 150 Aves, not only fifty, just as the Psalter numbers 150 Psalms and not fifty. Alanus’ opposition to the name ‘rosary’ stems from the “vain and worldly” origins of
rosarium,
corona, or
sertum. Even so, Alanus also found himself making use of the devotion in actual practice, whether consciously or unconsciously.
So, why did Blessed Alanus come up with St. Dominic (O.P.) receiving the Rosary from Our Lady? Perhaps it was just a practical one: Alanus wanted to attribute the prayer to someone venerable; and what better “author” can there be for the prayer than our holy father St. Dominic (perhaps Alanus noticed that Dominic of Prussia and Domingo de Guzmán share the same name…

)? Or perhaps, Alanus read Dominic of Prussia’s autobiography (the
Liber experientiarum), where Dominic wrote of a fellow (Carthusian) monk having a vision of Our Lady reciting the Psalter; in which case, he mistook the monk of the story to be a reference to Dominic (O.P.) Alanus himself also claimed to have visions of Mary, who ordered him to preach the method she taught to ‘Saint’ Dominic. The method that Mary teaches to Alanus - or so he says - based on the description (meditating on the “
articles of the life and Passion” of her Son), is actually suspiciously close to Dominic of Prussia’s method.
Now, despite Alanus’ protests that Dominic’s fifty Aves is unacceptably short, this is actually the main disadvantage of his devotion: fifty events is just too many for a lot of folks to remember by rote, and while versions of his narrative Rosary persisted into the 17th century, it ultimately lost to still shorter ones. The narrative form, however, remained and became successful in these shorter formats. Because of this disadvantage, a number of authors sought to revise and adapt Dominic’s method, merging it with Alanus’ three-part division of the Marian Psalter, for example by Justus Landsberg (d. 1535). But even this version was still too long for people to remember, which led to further adaptation and condensation by other writers, until the prototype of our modern Rosary - fifteen mysteries, punctuated by fifteen Our Fathers, with 150 Hail Marys - came out as a result.