Wherever John was writing the Jews were the enemy. In his account of the Lord’s dealings he used the word Jews referring to the Temple authorities. (The synoptics also dealt harshly with the Temple authorities, but they did not call them Jews.)
They were all Jews. The earliest Christians were about 98% Jews.
But when this book got around to being written, the writer had experienced a lot of trouble with the Jews. He therefore used this term of opprobrium. John got the reputation of being anti-semitic, which it still carries in many circles.
Words always carry more freight in peoples’ minds than the original intent of the author. The writer did not intend to condemn all the Jews since Jesus’ day, but by using the word for the people who fought Jesus and brought about his death, he got credit of it.
Most of the Jews I’ve known are more like (real) Christians than most of the Christians I’ve known.