There are no superhuman heroics involved here nor supersecret backroom deals. This is really just a simple story of good luck and timing, a spot on pivot and execution, and honestly brokered business relationships.
You can't duplicate the Instagram strategy because there was no strategy. These guys didn't build an app to flip. They built an app that was cool: to them, their friends, their investors, their users, and ultimately their suitors and acquirer.
Kudos to them.