im still going crazy over the (i feel) overlooked part of Isaac's lore that he was chronically ill. Terminally chronically ill, in fact. It mirrors Francoise. They both know what its like to waste away.
After his death, they used his chronic illness against him to spin tales that he was cold and driven by ambition.
I don't see ambition in Isaac, I see someone hellbent on trying to save someone he loves. I see someone willing to compromise his own values and needs out of love for that person. It's not because he can save her, its because he needs to. And failing this, he needs to do right by her. Even if it kills him. And it does.
In the scene after they run away from the second sabotaged machine, he looks more like himself, yes. There's more meat on his bones, more color in his skin.
But there was more life in his eyes the day prior when his body was still rotting but he thought he had a real shot at saving Francoise.
And he's still not okay. They show him faltering, nearly falling over, at least once. He's still weak, but he's pushing.
He also doesn't start pushing the revenge plot on the Addams until after Francoise tells him to cure Tyler instead and he goes a little off the rails over it. He's angry. Rightly so. The Addams have cost him his life's purpose. TWICE.
It's also my personal headcanon that the only reason Thing was able to "take over" in the end was because Isaac was done fighting. Francoise is dead. There's nothing left for him. There's nothing but anger and despair, and Thing, who is rumored to hold some of the good left in Isaac's heart, was so contrary to that that he could win. Before that there was enough "good" left in him that Thing still "accepted it". His intentions were pure enough (even if they did involve uhhh a lot of revenge and trying to kill Wednesday and Pugsley)
