I don't know the reason for dropping Kaye Wood, but I do know that Marie does sew. She has talked about this many times. When she was a child this is something special she shared with her mother Olive.
There is a real push to get teens and young woman interested in sewing. Perhaps Janome thinks they might relate better to Marie.
I think that celebrity endorsements are over-rated. I, like the rest of you couldn't care less what sewing machine any celebrity uses. If anything they risk losing a sale because the consumer doesn't like the celebrity they've chosen to represent their product.