How St Pius V "imposed" his liturgical reform

I was just flicking through Msgr Klaus Gamber's The Reform of the Roman Liturgy, and came upon this interesting passage, on pages 25-26:

In the Middle Ages nearly every church, or at least every diocese, had its own special Missal unless it had voluntarily adopted the Missal of the Roman Curia. No pope intervened in this matter. The parts which, more than any other, were subject to variation, were those parts of the Order of the Mass said in a low voice by the celebrant (so, the prayers at the foot of the altar, the offertory - also called the Minor Canon - and the prayers before Communion); in other words, the priest's "private prayers." On the other hand, the sung texts were almost everywhere the same within the Latin Church. Only some of the readings and prayers differed from locality to locality.

It was at this stage of development that the defense against Protestantism brought about the Council of Trent. It entrusted the pope with the publication of an amended Missal uniform for all. What exactly did St Pius V do? As I have already said, he took the Missal already in use in Rome and in many other places and he improved it, especially by reducing the number of feasts of saints. Did he make this Missal obligatory for the whole Church? No, he even respected local traditions only two hundred years old. Such a tradition was sufficient to free a diocese from the obligation of using the "Roman Missal." The fact that, even so, the majority of dioceses very quickly adopted to new Missal is due to other causes. But Rome exercised no pressure - and that in an age during which, unlike today, there was no talk either of pluralism or of tolerance.

 Contrast that approach with the imposition of Pope Paul VI's new liturgy.