The other half is what he was there for. The occasion is the "Fifth General Conference of the Episcopate of Latin America and the Caribbean." The reason is to buck up the Church in Latin America, which has been steadily losing people to pentecostal and evangelical Protestantism. That drain is one of the two major concerns of the bishops, the other being social injustice. The Catholic Church in Latin America and the Caribbean has been doing a slowly but steadily improving job on the latter; but that seems to have had little effect on the former. That's the dynamic I hope the Pope explores with the bishops.
On an intellectual level, that drain is almost incomprehensible to me. For reasons I've explained before, I have never found any version of Protestantism intellectually credible; for me, the only serious choices are Catholicism and Orthodoxy. That's cost me in a way, since my employment prospects would be much better in most Protestant churches than they are in the Catholic or would be in the Orthodox. Yet as I survey the sociological landscape of Catholicism, I can well understand why cradle Catholics who are not versed in ecclesiology, or indeed who are not well-catechized in any respect, would be seduced by pentecostalism and evangelicalism. Both forms of Protestantism take the experience of the individual believer very seriously; both lack the sharp division between laity and clergy so characteristic of Catholicism, so that formal ministry is more easily undertaken and more widely diffused; and congregations tend to be small, so that people know and support one another more closely than is the case in large, impersonal Catholic parishes. In short, these churches make people feel that they matter. And that matters a lot more, in marketing terms, than actually being "the" Church.
I don't know what the Church can do about that other than harboring more saints, such as Rose of Lima, or martyrs, such as Archbishop Romero. That's why the Pope is right to take on the Brazilian government about abortion and to emphasize the indissolubility of marriage. The same goes for the Church in the more "developed" countries of North America and Western Europe. What we need are more saints. We've had the sex-abuse scandals, the godawful liturgies, the casual heterodoxy, and the mass apostasy because we haven't had enough people, including enough clergy, who know and take seriously what it means to take up the cross and follow Jesus. We are Americans, or professionals, or nice people, or too many other things, before we are Christians. Only when that changes will the Church stop losing more people out the back door than she gains through the front. Only what can and would cost us terribly as individuals will build up the Body of Christ.