Just now seeing this. Thanks for the question.
The ideas behind the New Mass are no secret. They are right there in Sancrosanctum Concilium in VCII.
There were a few ideas I have heard. They wanted the Mass easily intelligible to the average layman, the the vernacular.
They wanted more participation on the part of the laity. There was perceived a passivity in the Old Rite and people saying rosaries, etc. and not saying the prayers of the Mass as the Priest silently recited Latin with his back to them.
There was a perception that the Old Mass had people showing up and going through the motions, not really involved or interested.
I personally think they could have simply put the TLM in English and made the Canon audible instead of changing the whole thing.
Obviously the innovators took the Mass of Paul VI , slapped a bad translation on it, added altar girls out of disobedience and CITH as well, EM's, lay lectors, bad music. none of which was mandated by VCII.