Yeah it didn't happen overnight or anything. I've been posting for about a year straight with WIP screenshots and fancy animations (https://twitter.com/aheze0) and also I've been doing a bunch of side projects on GitHub (https://github.com/aheze). Someone from the SwiftUI team also reached out, but I was further along with Photos so I went with it.
A good percent, a bunch of full time people in my team used to be interns. But I could have started out as full time if I talked with my manager, I just didn’t want to get stuck in a big company without trying other stuff first