This was a test launch, and normally in place of a real payload a rocket test will carry dead weight like concrete blocks. So Musk wanted to launch something a little cooler than rocks.
It's not billionaire playboy wasting hundreds of millions of dollars, he's actually saving hundreds of millions, billions of dollars for the space industry - this rocket LANDED after it launched and is reusable - a first. All launches before this by all other space agencies, the boosters and all stages just burned up in re-entry. He's launching at lower cost already than NASA and the military, and owns another company with serious plans to mine asteroids for precious metals that are rare and almost cost prohibitive to extract from the earth.
Seriously, there were better choices of billionaires with no political experience, but this guy is too busy with human progress to be president anyway, not interested.
It was his own car, too haha