Although Michael Bublé has had extensive vocal study, he has not had any kind of formal music education that would enable him to write the styles of music that he performs (he doesn't read or write music, or play an instrument).  He is professionally adept with lyrics, however, and works with multiple cowriters skilled in music composition, which for obvious reasons limits their output.

Consider that the great Frank Sinatra also had a similar meager songwriting output, always with cowriters.  Clearly, the vast majority of his recordings were written by others.  In that era, singers and composers were almost entirely separate — singers didn't write, songwriters didn't sing.  Much of Bublé's repertoire necessarily comes from that era, and he couldn't have composed any of it, since he would even be born for another twenty years.

Michael has written 8 songs out of his whole catalog. He's just a sensational cover singer, such as the likes of Joe Cocker, Three Dog Night, Whitney Houston and others.

"Stolen"?

Honey, those are called "covers," not "stolen". Covers are a time-honored tradition, especially when it comes to Christmas songs.

Bublé specializes in classics; he has that kind of voice. You have a lot to learn.