The words "whole country" are a metaphor for the people who live in the country and a generalization that refers to a great number of people, not to every single person. Alternate translation: "Many people from Judea and Jerusalem" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-hyperbole]])
They did these things at the same time. The people were baptized because they repented of their sins. Alternate translation: "When they repented of their sins, John baptized them in the Jordan River" (See: [[rc://en/ta/man/translate/figs-activepassive]])