The document was the result of a commission established by Pius XII in 1946 to "restore" the Holy Week rites to their ancient times of observance. Previously, ceremonies such as the Easter Vigil were celebrated on Saturday morning; the new Ordo moved them to the night to better reflect the scriptural timeline.
For those interested in exploring more about the Ordo Hebdomadae Sanctae Instauratus and its significance, the following resources are recommended: ordo hebdomadae sanctae instauratus pdf install