Braun had successfully published font packs for the Amiga personal computer when he met Will Wright at a pizza party hosted by Chris Doner in 1987. Wright had been unsuccessful in finding a game publisher for his city-building game SimCity. Braun already had a wire frame jet fighter simulation game, now known as SkyChase, which he hoped to publish. When he saw SimCity he told Wright that the two games would give them critical mass to start a new games publisher of their own. They named the company Maxis.
Wright had been an employee of Brøderbund when he first developed the concept, so Braun and he had to return there to clear the rights to SimCity. Brøderbund had just set up a new distribution office to counter the Electronic Arts (EA) Affiliated Label program. Brøderbund executives Gary Carlston and Don Daglow saw SimCity, recognized its potential and urged Braun to sign a distribution deal with Brøderbund for the game. Braun wanted the jet fighter game included in the deal, and Brøderbund agreed.
The first five years of Maxis' history saw them remaining with Brøderbund, before Braun added a dedicated sales force to Maxis in preparation to taking the company public. The company's IPO took place in 1995. In 1997, after setbacks on a series of secondary titles, Braun and Wright sold Maxis to Electronic Arts for US$120 million in stock. The deal made Braun the largest shareholder in EA at the time.
Since 1997 Braun has continued to make investments in a wide range of software and technology companies in the United States and in Israel. In the late 1990s he suffered a broken hip in an accident riding his unicycle, but recovered fully.
He left Maxis after finishing The Sims and is now part of Red Mile Entertainment.