St Peter and the other apostles were the leadership group set up by Jesus.
The pope and the bishops are the continuation of that leadership group

The C.E.O. of the group is the pope.
And when the bishops Inc. have a board meeting with the pope,
- especially when they hold an ecumenical council -
then the bishops Inc and the pope together have C.E.O. authority at its highest level

So far, so good.

But what happens when a pope calls a board meeting
and some of the bishops are opposed to the meeting
.... before the meeting
.... during the meeting
.... and after the meeting?

This is what happened 53 years ago when John XXIII announced
he was having a board meeting.
A powerful group in the Curia were anti-meeting

And then it got even stickier:

A member of the anti-meeting group became pope ..... Benedict 16.
He used to be pro-meeting. But then he crossed the floor

So where does that leave us?
What happens when a pope goes against the decisions of a very recent ecumenical council?
Is not going against the decisions of Vatican 2 an act of ....s c h i s m ???

Which is what this letter to all bishops is about  (worth re-reading)