OK, Christmas music didn't really need saving (other than when the Puritans ruled England and its American colonies in the mid 1600s and banned Christmas). But William Sandys put together the first modern collection of Christmas Carols in his 1833 book, Christmas Carols Ancient and Modern. Published just as the Victorian period was getting under way (the Victorians were famously sentimental about Christmas, among other things popularizing the idea of the Christmas Tree), Sandy's book made famous the core of what we recognize as Christmas Carols: God Rest You Merry Gentlemen, The First Noel, I Saw Three Ships, and Hark the Herald Angels Sing.
Here is a little playlist of Sandys' collection. Yeah, he didn't really "save" Christmas music, but he sure wrote it all down.