Many are the orthodox Catholics who have explained why it is apt to change "for many" to "for all" from Fr. William Most, to Catholic Answers to Roman Theological Forum..if my memory was better I could list many more (I do prefer the 1962 Roman Missal btw)
It has to do with the sufficiency of the Sacrifice. Jesus died so that all could be forgiven. Unfortunately, the Sacrifice will only be efficacious for some. But that does not mean that the Sacrifice is limited to "many."
SD