Read John 19:31 Using Other Translations
The Jews therefore, because it was the preparation, that the bodies should not remain upon the cross on the sabbath day, (for that sabbath day was an high day,) besought Pilate that their legs might be broken, and that they might be taken away.
Since it was the day of Preparation, and so that the bodies would not remain on the cross on the Sabbath (for that Sabbath was a high day), the Jews asked Pilate that their legs might be broken and that they might be taken away.
It was the day of preparation, and the Jewish leaders didn’t want the bodies hanging there the next day, which was the Sabbath (and a very special Sabbath, because it was the Passover). So they asked Pilate to hasten their deaths by ordering that their legs be broken. Then their bodies could be taken down.