There's the popular notion that, beneath the bluster and bombast of a raging narcissist, there is this deeply wounded and insecure person. After all, what else could explain the unchecked ego, unmitigated entitlement, and grandiosity of narcissism? It must be overcompensation.
From two tweets: https://twitter.com/JoshuaGrubbsPhD/status/891974226068086784. Copy modified slightly.