Most of this paragraph seems a factual account of the two decades prior to Pope Benedict’s motu proprio of 2007.
First, the sense that the use of the 1962 Missal was somewhat elevated from a special permission to a centerpiece of a liturgical culture within the Church:
Many in the Church came to regard this faculty as an opportunity to adopt freely the Roman Missal promulgated by St. Pius V and use it in a manner parallel to the Roman Missal promulgated by St. Paul VI.
By this century, the Church arrived at a situation that required, in Pope Benedict’s view, some juridical parameters, as he explained in the accompanying letter to Summorum Pontificum.
In order to regulate this situation at the distance of many years, Benedict XVI intervened to address this state of affairs in the Church. Many priests and communities had “used with gratitude the possibility offered by the Motu proprio” of St. John Paul II. Underscoring that this development was not foreseeable in 1988, the Motu proprio Summorum Pontificum of 2007 intended to introduce “a clearer juridical regulation” in this area.
Was this unforeseen, that a new generation would find in the traditional Latin Mass, a draw to a deeper spirituality and/or religious observance?
In order to allow access to those, including young people, who when “they discover this liturgical form, feel attracted to it and find in it a form, particularly suited to them, to encounter the mystery of the most holy Eucharist”,
And so an indult and concession to a small number of elderly clergy and a somewhat larger number of those leaning to schism had sprouted a life of its own within the Church.
Benedict XVI declared “the Missal promulgated by St. Pius V and newly edited by Blessed John XXIII, as a extraordinary expression of the same lex orandi”, granting a “more ample possibility for the use of the 1962 Missal”.
And so we arrive at 2007. Anything amiss or confusing yet?
The quotes here are all from Pope Benedict XVI, his Letter to the Bishops on the occasion of the publication of the Apostolic Letter “Motu proprio data” Summorum Pontificum on the use of the Roman Liturgy prior to the reform of 1970, 7 july 2007: AAS 99 (2007) 796-797
Here are the important links: