He also doesn't have the cognitive and emotional capacity to lead. Intellectually, he is very limited.

He doesn't understand the basics involved in this, or any other situation that goes beyond preening for cameras and adoring crowds. https://twitter.com/JRubinBlogger/status/1247330671695101952

So it's not just (if at all) fear that may keep him from performing his duties, but his inability to really grasp what is happening, what needs to be done, and what is required of him.

He is playacting a president. Just as he playacted a successful businessman, a caring husband, a doting father. It's all an empty facade. He knows it too, somewhere within, and it terrifies him. That's why he so easily projects it on others when he accuses them of fakery.