Among that throng of people is Bret Johnsen, who has served as the company’s only chief financial officer and acted as the quiet architect behind the largest IPO in history. His stake in the company has now exceeded about $1.4 billion, meaning SpaceX going public made him a billionaire overnight.

Musk brought on Johnsen as CFO in 2011 explicitly to guide SpaceX through its IPO.

“His experience will be invaluable to SpaceX as we implement the financial standards and processes needed to allow for the possibility of becoming a public company,” Musk said in a statement at the time of Johnsen’s hiring.

Since joining SpaceX, Johnsen has been the man working behind the scenes, making few public appearances, but leading the company through its transition from startup with a 10% chance of success—in Musk’s words—to a company bringing in $18.7 billion in revenue last year.

Johnsen must now see SpaceX through its next era, delivering on its myriad promises surrounding satellites, internet, AI, and space travel.

“I tell people it’s hard to be a space company and not have assured access to space,” Johnsen said in a recent interview with investor Gavin Baker. “We’re now lowest cost per kilogram to space ever in the industry. So it is definitely at the core of what we do, and it’s the enablement for all of the other businesses, whether it’s Starlink or direct to cell very soon or now AI compute.”

Johnsen’s unique role following SpaceX’s IPO

Prior to SpaceX’s IPO that raised $75 billion, Johnsen was already busy navigating the space company’s merger with xAI, Musk’s AI company, which it acquired in February in an all-stock transaction valued at $1.25 trillion.

He also helped broker a deal with Anthropic, which agreed to lend a chunk of its compute capacity to SpaceX’s Colossus data centers in Memphis, Tennessee. The deal defied Musk’s public critiques of Anthropic, which he claimed “hates Western civilization” in a February social media post.

But following SpaceX’s launch as a public company, Johnsen’s job will look a little different than those of typical CFOs. Because the company set aside 30% of shares for retail investors, a much higher allocation than typical IPOs, Johnsen will have heavy lifting to do in articulating SpaceX’s role in the space and AI sectors.

“Most IPO CFOs have to clean up the accounting, tighten controls, and sell the story of the firm,” Shivaram Rajgopal, professor of accounting and auditing at Columbia Business School, told Fortune.

But because of Musk’s moonshot promises of colonizing Mars—as well as a potential merger between SpaceX and Tesla—Johnsen will have the added responsibility of selling what is essentially a tech conglomerate to Musk’s followers and retail investors.

“He can do all of this because Musk has a massive retail investor following, and the institutions getting in now are hoping to make a buck riding the momentum before the cold reality of fundamentals catches up in a year or two,” Rajgopal said.

Who is Bret Johnsen?

In some ways, Johnsen is a foil to Musk. While the CEO makes headlines with social media posts with far-right assertions and anti-immigrant stances, Johnsen has about 3,000 followers on X and no public posts. The CFO seldom makes public speaking appearances. One SpaceX employee described Johnsen to The Information as “a boring suit.”

Johnsen, 57, is a Los Angeles native who studied accounting at the University of Southern California, where he now sits on the board of trustees. He stayed in California to get his master’s degree in finance from San Diego State University.

Before SpaceX, Johnsen held a senior finance role for about a decade at Broadcom, a semiconductor infrastructure firm. He then became CFO at Mindspeed Technologies, which also makes networking and telecommunications chips.

During the 2008 Financial Crisis, he cut jobs and spending, restructured the company’s debt, sold its technology patents, and raised cash through selling additional company shares. In his three years at Mindspeed, he said he increased the valuation of the company 15-fold.

“We were headed into the worst economy of our lifetimes in the second half of 2008,” he told the Orange County Business Journal. “It gave me the chance to make a lot of changes that I thought really needed to be made.”