'Unbreakable' is basically a pop version of the 'Unbelievable' song.
American producer DJ Premier was the guy who created the 'Unbelievable' song.
DJ Premier seems to be connected also with Rodney Jerkins (who created the 'Unbreakable' song).
Note that Michael Jackson himself announced to Sony Music (in the midst of the 'Invincible' album sessions) that he was about to leave them.
So, both parties are to blame for the lack of promotion of that album.
On the 'Invincible' album, Michael Jackson took many undue songwriting credits for himself, but he also allowed members of Rodney Jerkins' team to take many undue songwriting credits for themselves.