Watching Trump post-signing it's clear he's losing his grip on reality , or perhaps that reality is losing its grip on him. You can see it in his body language "You mean by signing here, I can undo everything that black guy worked so hard for, and I can make millions of people cry? Wonderful! I'm God!"
He knows he is invincible. He knows he creates his own reality. He knows people will do whatever the fuck he wants done. That isn't actual reality, but it is his reality, just as Medieval Kings used to torment and humiliate people around them for jaded amusement, so does Trump, and he is only going to get worse.