[bottlepalm]

Because it's Elon who said "ok, build it." There's no one else except him with that power and/or the guts. Even landing a rocket the government had given up on, and no company was even trying until he did. People were calling the 'chopstick' landing system a dumb idea until today.

It's not like engineers don't come up with wild ideas all the time to their leadership, but is the leadership good enough to understand the good ideas from bad ones? Take the risk, spend billions to actually execute?

Elon has enough of a physics/engineering background to ask the right questions, understand the trades engineers put in front of him, and make the risk/reward calculation to make the right decisions the ends up winning.

To get what SpaceX has you need strong technical leadership all the way up the chain. Many companies don't. Their CEOs are experts in legal, PR, finance, etc... They make poor technical decisions.