I think it's mostly greed (the life insurance payout he gets on her death), spiced by hatred of her (for not having the decency to die and make him rich years ago ) as well as rage against his inlaws for keeping him from what's righfully his-ie, the life insurance. But it's fear too, or why else has he stated that Terri is to be cremated IMMEDIATELY upon death?
I think it's mostly greed (the life insurance payout he gets on her death), Michael Schiavo's attorney claims that no such life insurance policy exists. This should not be a hard fact to determine definitively, one way or the other.
When Terri dies, there will be an autopsy regardless of whether she is cremated afterward.
It's very tempting to make arguments based on perceived motives of opponents, and most of us do that, but it's not really the best or most effective way to argue.