Then why, SF, the continued negotiations with Karpov after 1975? What may be clear to you does not align with his subsequent actions.
JD: Because people are complicated and Fischer especially so. People often do things for more than one reason and those reasons may contradict each other.
My guess is Fischer wanted to play Karpov in 1976 but still felt ambivalent about it. If he lost to Karpov, he would have to live with that. If he ratcheted up demands for playing conditions until Karpov's side refused, he could say he was still the champion and blame the Karpov people for preventing a match.
The latter course was safer for him in the short-term, though long-term it sent him into a self-imposed exile and sad life.
People, not just Fischer, do stuff like this all the time.
"Fischer's list of match conditions in 1975 were what he believed would produce the finest chess and the most equitable result"
He just forgot about demanding that the challenger must win with a margin of two games to get the title back in 1972.