Mar 1:5 Then all the land of Judea, and those from Jerusalem, went out to him and were all baptized by him in the Jordan River, confessing their sins.
In Mark 1:5, John the Baptist is preaching and baptizing. He becomes very popular. The text reads “all the land of Judea” became baptized by him. They all confess their sins.
The language is hyperbolic, and not meant to include every individual. John did not complete an 100% conversion of all of Judea.
What this shows is a common convention in communication. “All” can refer to “most”, “many” or even be limited to a small group (by context). This illustrates the most import concept in reading comprehension. Context determines meaning. It is a mistake to assume hyperbolic sounding phrases are unlimited unless the context calls for it.