Not all of us learn the same way, or grasp things the same way, so too the same truths of the Catholic Church are presented in a different way, by different Catechism authors.
There are two Catechisms that the Catechism of the Council of Trent, and the Current, CCC, which have a semi official status. But because of all the languages and Cultures that the Catholic Church is composed of there are Catechisms that have been endorsed or authorized by National groups, as was the case for the Baltimore Catechism in the USA. However while these Catechisms did carry the endorsement of the Catholic Bishops of various countries and language groups, that did not stop the publication of other Catechisms which all in the past had to be reviewed, and given an Imprimater, or permission to be printed and sold as a book that did not contain error. (More on Imprimaters sometime later, as they do not make a book an “official” Catholic Book, as some anti-catholics mislead people into believing.)
The Catechism of the Council of Trent was published to counter some of the new Theological ideas coming from Luther, Zwigely, and Calvin, as well as to form a uniform manner of learning the Faith. It is one of the earliest Catechisms in print. You have to remember that prior to Luther’s day, all books were either copied by hand, (Usually in Monastic settings) and very expensive. Most people could not read, because books were so rare, Newspapers and Magazines did not exist. After Guttenberg invented movable type, and books could be printed much easier, and at a much lower cost, it became within the reach of many to learn to read, and own a book. It is also important (I think) to note that the first book that was printed with movable type, was the Vulgate, a Catholic Bible.
I think what some non-Catholics don’t understand, being taught that the Catholic Clergy has a stangle hold on people’s minds, and forces Catholics to follow a strict blind obedience. The reality is that Catholics have quite a bit of freedom to read a variety of books which look at Cathoic teachings from a variety of viewpoints.