Complex sentence: On December 1, BTS won their third daesang, Artist of the Year, at the 2017 Mnet Asian Music Awards, thus becoming the first ever K-pop artist to win the award two years in a row.
Split into simpler sentences: On December 1, BTS won their third daesang, Artist of the Year, at the 2017 Mnet Asian Music Awards. By doing this, BTS became the first ever K-pop artist to win the award two years in a row.