They thought they could flip Palin. Failing that, they shift blame to her.
Yes, they scape-goated her for his lousy campaign. I believe Sarah Palin is responsible for our good President Trump, however. She pierced the darkness, got people involved, spoke the Truth. Prophets speak the Truth, and they have always killed them. Have throughout history. DJT is very unusual in that he is a street fighter and doesn’t give a fig about their vitriol.
I think this is very poor of John McCain - a real jerk until and after the very end. But it is in character.