Why does Protestant Bible have 7 fewer books than the Catholic Bible?

Many folks are puzzled by the fact that the non-Catholic Bible has seven fewer books in its Old Testament than the Catholic Bible. For an extensive discussion on this topic, watch this video from Fr Martino:

Fr Martino on OT Canon

 The condensed version is:

In 2nd Century BC, Jewish scholars translated the  Hebrew Scriptures into Greek. Seven of the books were originally written in Greek, not Hebrew, but the 70 rabbis doing the project kept them anyway.

In 400 AD, St Jerome translated the Bible into Latin (called the Vulgate version). He opined that only those originally written in Hebrew should be part of the Canon, the other 7 should be tossed out. St Augustine weighed in, and said no, we should retain them all. The Council of Hippo in 393 confirmed that all 46 OT books shall remain in the Canon.

During the reformation, Martin Luther raised the issue again, and said the 7 Greek books should be dropped. A few years later, the Council of Trent reaffirmed the Church's Canon of 46 OT books. Luther & his followers decided to stick with only 39 books in their OT. So, today we have 2 separate versions of the OT.