Mariah Carey is the undisputed Queen of Christmas, with her 1994 holiday original “All I Want for Christmas Is You” topping the Billboard Hot 100 multiple times over the last few years and ranking as the most popular song of all time on the Billboard Holiday 100.

But how did it happen? How did a song from 1994 that didn’t register on the Hot 100 at first become Carey’s 19th No. 1 in 2019, making her the first artist to have a Hot 100 topper in four different decades?

The latest episode of Billboard Explains breaks down the history of Mariah’s modern Christmas classic and the factors that contributed to its slow and steady climb to the top over the years, from Hot 100 rule changes to partnerships to blockbuster streaming numbers.

After the video, catch up on more Billboard Explains clips and learn about how the Hot 100 works, how R&B/hip-hop became the biggest genre in the U.S.how festivals book their lineupsBillie Eilish’s formula for success, the history of rap battlesnonbinary awareness in musicthe Billboard Music Awardsthe Free Britney movement, rise of K-pop in the U.S., why Taylor Swift is re-recording her first six albums, the boom of hit all-female collaborations, how Grammy nominees and winners are chosenwhy songwriters are selling their publishing catalogs, how the Super Bowl halftime show is booked and why Olivia Rodrigo’s “Drivers License” was able to shoot to No. 1 on the Hot 100.