I suspect that he's so rattled that he can't keep his enemies list and his list of donors separate anymore.
@Tarnagh @BenA @JV3MJD You're right. Also, as some here pointed out, it was written with lower case letters which T is unable to do.
Likely one of his campaign staffers, who have been begging him to shut up the insults and try to behave like a president or just a normal person, posted it on his behalf. And when he sees it, enraged, he'll fire the staffer and go back to taunting Kemp.