Having inherited a family fortune and, effectively, the leadership of the Liberal Party, Justin enjoys a more privileged life than you or I ever will. As we sometimes see with children of celebrities, or those who achieve fame too young, arrested development sets in.
To wit, such people do not mature because they do not have to.
As a rough estimate, I would assess Justin a mental age of about 15.
I do not mean a precocious 15, either. In fact, I mean a particular sort of teenager, with which you might be familiar.
I mean the kid in the class who adores the sound of his own voice, who stands in awe of his own intellect, and whose overall obtuseness is obvious to everyone but himself.
He is the sort of self-promoting, mean-spirited virtue-signaler who is always leading some politically correct campaign, just so he can make a speech in assembly or get himself interviewed by the local news.