Earlier this month, Chris Lattner announced that he was leaving Apple to lead Tesla’s Autopilot software team after a decade at the Cupertino company where he led the development of the Swift programming language and developer tools.

There have been rumors about why he was leaving Apple, but the software engineer has now broken the silence to kill the rumors and disclose why he joined Tesla.

Some had speculated that Apple’s closed and secretive culture had driven out Lattner like it had with a few others in recent years. The constant patent battles are driving some of the employees mad and taking away the focus on products.

For example, long-time Apple UI designer Bas Ording who joined Tesla last year said that the time spent on patent lawsuits was part of his decision to leave the company:

“Because my name is listed on patents, I increasingly had to appear in court cases versus HTC and Samsung,” he said, “That started to annoy me. I spent more time in court than designing.”

While Tesla is still somewhat of a secretive company, the company has a different approach than Apple and open-sourced all of its patents.

But Lattner said that his decision had nothing to do with “openness”:

Yesterday, he clarified his thought process for leaving Apple in a comment to MacRumors:

I’ve been writing code for more than 30 years, and 16 of those years have been in the developer tools space. I love it, but I am ready to move on to something else. Autopilot is clearly incredibly important to the world because of its ability to save people’s lives (and increase convenience). It is also a very, very hard technology problem and my experience building large scale software and team building is useful. Of course, I’ve also been a huge Tesla fan for some time.

Useful indeed. Lattner has experience leading a team strong of ~200 software engineers and his years building tools for software developers made him a respected figure in the community. It makes him an interesting candidate to lead Tesla’s growing team of “hardcore software engineers“, as CEO Elon Musk called them, who are building the software for Autopilot.

We recently reported that Tesla hired several video game programmers to work on the system.

Lattner added that the opportunity to work with the team was “irresistible”:

This was a very difficult decision, because I care deeply about the technology and people at Apple and because I could see myself staying there for many more years. In the end though, the opportunity to dive into a completely new area and work with the amazing Tesla Autopilot team was irresistible.

It will be interesting to follow the team’s progress as it currently releases the first phase of ‘Enhanced Autopilot’ and work toward a complete demonstration of a fully autonomous platform driving coast-to-coast by the end of the year.