“I believe he knew the assassination was planned.”
I won’t go so far as to say he helped plan it, because he’s addled brained. But he definitely knew.
Also who knew were Nikki Haley and Mike Pompeo. They probably already had their campaign buttons and bumper stickers ready for distribution.
It could not have gotten so far, the USSS performing so BADLY, the FBI not working and warning, and all the local LEs cut out of the planning picture without his tacit nod, whether he cogently knew it or not.