Why did the Second Vatican Council ignore the issue of Communism?

[UPDATE 2-28-3: This article has undergone significant revision in light of new information. See especially the Endnote] 

My idea for this post came from a recent article on the Ignatius Press blog, which had a link to a Catholic World Report article titled "Why did Vatican II ignore Communism?" When I saw the title of this article I was completely stunned. Did Vatican II really ignore Communism? That's outrageous! But if this is true, then I really want to know why, because that comes off as scandalous.

I am a big fan of Catholic Social Teaching, the traditional Catholic form, not the modern distortions, so I'm well aware of how the Popes in the 1800s and the early 1900s rabidly and repeatedly condemned Communism in the strongest terms. So when I heard that Vatican II ignored Communism, something seemed very wrong. To get an idea of what the Church has said in the past, well before Vatican II, consider the following quotes from Pope Pius XI in his 1937 encyclical Divini Redemptoris: On Atheistic Communism,

This modern revolution, it may be said, has actually broken out or threatens everywhere, and it exceeds in amplitude and violence anything yet experienced in the preceding persecutions launched against the Church. 

This all too imminent danger, Venerable Brethren, as you have already surmised, is bolshevistic and atheistic Communism, which aims at upsetting the social order and at undermining the very foundations of Christian civilization.

In the face of such a threat, the Catholic Church could not and does not remain silent. This Apostolic See, above all, has not refrained from raising its voice, for it knows that its proper and social mission is to defend truth, justice and all those eternal values which Communism ignores or attacks. Ever since the days when groups of "intellectuals" were formed in an arrogant attempt to free civilization from the bonds of morality and religion, Our Predecessors overtly and explicitly drew the attention of the world to the consequences of the dechristianization of human society. 

In fact, the most persistent enemies of the Church, who from Moscow are directing the struggle against Christian civilization, themselves bear witness, by their unceasing attacks in word and act, that even to this hour the Papacy has continued faithfully to protect the sanctuary of the Christian religion, and that it [the Church] has called public attention to the perils of Communism more frequently and more effectively than any other public authority on earth.

Just in these few brief paragraphs from Pius XI, any Catholic can see quite plainly that Communism, particularly the form coming from the Soviet Union (Moscow), was ravaging nations and a threat to the whole world. It was nothing to to joke about, and that's why Pius XI said the Church 'could not keep silent about' Communism. This warning was given in 1937, so the USSR was still on track to cause a lot more damage for decades to come, spreading communism all over the world, notably in Eastern Europe, China, Vietnam, Korea, Mexico, Spain, and Cuba. This ravaging took over largely Catholic nations and lasted into the 1990s. This means that during the Second Vatican Council, Communism was still a juggernaut, not something to be ignored. 

So why did the Council remain silent on the issue of Communism? 
[The last section of the original post was removed for criticizing Vatican II for ignoring Communism. This was wrong, and so was Catholic World Report for suggesting it.]

*   *   *   *   *   *   *   *   *

[UPDATE 2-28-3] 
I have taken up the task of reading the Second Vatican Council documents for myself, and I came across some information in them that in fairness should be mentioned. In one of the key documents of the Council, Gaudium et Spes, I saw the following being taught:

19. ... [M]any of our contemporaries have never recognized this intimate and vital link with God, or have explicitly rejected it. Thus atheism must be accounted among the most serious problems of this age, and is deserving of closer examination. ...

20. ... Not to be overlooked among the forms of modern atheism is that which anticipates the liberation of man especially through his economic and social emancipation. This form argues that by its nature religion thwarts this liberation by arousing man's hope for a deceptive future life, thereby diverting him from the constructing of the earthly city. Consequently when the proponents of this doctrine gain governmental power they vigorously fight against religion, and promote atheism by using, especially in the education of youth, those means of pressure which public power has at its disposal.

21. In her loyal devotion to God and men, the Church has already repudiated (16) and cannot cease repudiating, sorrowfully but as firmly as possible, those poisonous doctrines and actions which contradict reason and the common experience of humanity, and dethrone man from his native excellence.

16. Cf. Pius XI, encyclical letter Divini Redemptoris, March 19, 1937

This passage is significant because it does address Communism, at least the central pillar of it (atheism), but without using the term "Communist." This is made especially clear by the fact endnote #16 explicitly references the Encyclical quoted earlier by Pius XI on Atheistic Communism. So Vatican II did not ignore Communism, contrary to what the media outlet had led me and others to originally believe. The Council could have been more explicit and gone after Communism more directly, but it's wrong and unfair to suggest the Council ignored it. Now whether later generations of Catholic theologians and priests actually cared enough (or were aware enough) to read the encyclical of Pius XI and heed his warnings is another story.