Reconstructing the past from very fragmentary evidence is no easy thing, as I'm sure we all know (I can barely remember what happened two hours ago). So any piece of new evidence can lead to enormous changes in our understanding.
The earliest (possible) reference to the Jews in Egyptian records (that I'm aware of) is to the Habiru(?) sometime in the 13th(?) century B.C. Palestine is mentioned 3 centuries earlier, when it was an Egyptian colony, but it was not then inhabited by Jews.