She knew what was on the tapes. If she didn't mean what she had said or changed her mind, she had plenty of time to correct her remarks herself.
I do not know why Jackie made the tapes in the first place or why Caroline released them--but one thing's certain: they'll make lots of money.
If I remember correctly, Caroline sold most of Jackie's jewelry and made a lot of money. She did not donate the jewelry to a museum. QVC sells reproductions of her jewelry, and they carefully explain the history of each piece.
Caroline traded the tapes in exchange for the studio NOT to air the documentary about the family. The one starring Katie Holmes.
Jackie made the tapes with a stipulation the be held for 50 years or so after her death. Caroline overturned her wishes.