On the blog Catholic and Enjoying It!, Mark Shea says (of Vatican 2):

The fact is, the Spirit called the Council, so it was the best thing that could have happened

which raises two questions: (1) Was the Council called by the Spirit? (2) And was it the best thing that could have happened?

(1) The first question can be addressed in two ways. Firstly, we can conclude that Vatican 2 was initiated under the inspiration of the Spirit, because the Pope who called for a Council said it had been called for by the Spirit. John XXIII's address at the opening of the Council clearly makes such a claim. Secondly, on more general grounds we should expect that all properly convened Ecumenical Councils are called for by the Spirit. The Church has been given power to call Councils, and the source of that power is in the Spirit.

(2) Was it the best thing that could have happened? I.e. not just a good thing, or a very good thing, but the best thing, just because it was the Spirit that called it?This seems dubious to me.

For one thing, God's good can't be measured on a scale, since no such external scale exists. Creation in Gen 1 was declared to be very good, not the best, and that comparison took place between the whole of Creation, and its parts. And how could God be incapable of adding further good to something?

For another, since God is wholly free, He can give greater or lesser goods, just as He pleases. Unlike humans, when God gives a lesser good, it does not follow that there is anything imperfect or lacking in that lesser good.

So it seems to me that God was free not to call the Council, and instead could have chosen to do something else (just as John XXIII was simultaneously free not to call the Council).