For one thing, we learn now that it was not his own money.
For another thing, this is supposed to be a religious ceremony celebrating a young person's obligation to fulfill G-D's commandments. That is not done with a vulgar and lavish display of excess.
I have heard about another very wealthy family that celebrated their son's bar mitzvah by giving him $1 million--all to be distributed to various worthy charities.
He earns it making body armour. I thinking he could have found somewhere to donate $9 million worth of vests, the world being what it is, and held the Bat Mitzvah to $1 million, like all the rest of us.