Jesus explained his death and resurrection in advance to the Apostles, but it was the Holy Spirit who enlightened them to understand. He enlightens us as well when we open ourselves to receive Him.

According to the article, found via Catholic Online:

Orthodoxy and unity were key reasons the sisters were attracted to the Catholic faith. Many of them were troubled by the Episcopal Church’s approval of women’s ordination, the ordination of a gay bishop and what they regarded as lax stances on moral issues.

The nuns strove to be a “witness for orthodoxy” within the Episcopal Church, but Mother Christina Christie, the community’s superior, said that by not doing anything more than that they sent the wrong message. They resisted pleas to stay as well as their own thoughts of joining the more orthodox Anglican American church, newly formed in a much publicized schism with the Episcopal Church over issues of orthodoxy, such as the consecration, in New Hampshire, of the openly homosexual bishop, Gene Robinson.

In the end, however, the Holy Spirit directed them to the Church — for some time, the sisters individually were secretly contemplating Catholicism. When they realized this, the decision was easier to make. Said Mother Christina:

This is very much the work of the Holy Spirit.

There was some earthly help, too, although, of course, the Holy Spirit was working there as well: As it turns out, the nuns greatly admire Pope Benedict XVI.