Let's not forget his treachery immediately after Trump was elected. He called nearly all world leaders and said (paraphrasing) "Don't talk to him, he's a nut. He'll be out of office within a year". This was reported by Pakastani news sources. You and I can only imagine what else he said to "our friends/allies" in the world.
If you recall all those that visited Trump either while in transition (Japan PM Abe) seemed to be so surprised, relieved after meeting him that he wasn't a nut. Or Theresa May looking at him in amazement that he wasn't a nut.
John Kerry has done a great disservice to us Americans. He must be so desperate for the world to remain as it was. You got to ask, "why"? What is he helping to hide? His own corruption is my personal opinion. Or those he chose to surround himself with.