Because Vatican II documents in and of themselves many were written so vague as to allow for wide and varied implementation......especially with regard to religious life, and the Liturgy. VAtucan II never called for Orders of nuns to discard the traditional habits. It called for the adaption of SOME habits which were no longer practical ( example, it was impossible for Daughters of Charity with their large starches cornets to drive a car, or likewise a few other Orders and congregations of sisters whose headpieces impaired vision either when driving or just walking. These were the adaptions requested (not ordered) by the Council. Nearly all religious Orders of sisters took wide license with these directives, and adapted themselves eventually out of existance due to radical liberal "reforms" which were despised from the beginning by potential aspirants, and even by members of the Orders who left en masse.
Same with liurcy....so many variations, adaptions, permissons, abuses, experimentaiions that it can truely be said that there is no more true "Catholic Mass", except where the Roman Rite is celebrated.
The Council documents many of which were written to give some wide room for freedomm of implementation, which has proved a disaster.
I hope the next Pope pays little attention to Vatican II and it's "reforms" but rather finally realizes the damage and wreckage it has caused.