I suspect he knows enough to take them all down, that's why they want him out of the way. Knowing him he also has an in case of sudden death leak this document plan, otherwise they would have already tried to end him.
WE WANT ALL OF YOUR PARTY TO GET BEHIND FUNDING UKRAINE. WE STILL DON'T KNOW WHAT ZELENSKY HAS OVER OBAMA AND THE REST OF YOUR ELITE, WE JUST KNOW HIM REVEALING IT WOULD COST YOU THE ELECTION. ONCE TRUMP WINS ZELENSKY'S CASH COW DIES.