It has become a power struggle for him. But I gather that he is getting financial support from "right-to-die" zealots. He can't back down now, because his ego is fully involved.
I doubt he's getting financial support from right-to-die organizations. Those organizations generally recognize the need for clear directives from the patient. Terri Schiavo makes a lousy test case for right-to-die law, since very few people think that the word of a slimy guy like Michael Schiavo should suffice as proof of a patient's wish not to have life-prolonging treatment in the event of severe disability. I firmly believe in the "right to die", and would certainly wish to be euthanized quickly (not starved and dehydrated to death slowly) if I were in Terri's condition, but I sure wouldn't give Michael Schiavo a penny.