Jove's Huge Tree and the Shrub

"As for myself, I stand as Jove's huge tree,
And others are but shrubs compared to me;
All tremble at my name, and I fear none.
Let's see who dare impeach me for his death" (5.6.11-14)

It is ironic that Mortimer's thinks he's untouchable and omnipotent when in the end, it is a "shrub" that orders him to be killed by quartering. A boy not even yet in his teens, a "shrub" compared to "Jove's huge tree," has enough power to destroy all those who stood against the King, regardless of how un-kingly the King was. I can't imagine how big of a smack in the face Mortimer received when he realized that the very king he enthroned, a pre-adolescent boy, would be the very king that would shape his demise. What's the saying? Oh yeah: don't judge a book by its cover.