That's SOP for SpaceX, right? Take proven technology and actually make it work commercially.
Given that the primary lender and customer is the government, "commercially" is a stretch there.
7 launches this year. 3 Nasa. 4 commercial.
Pretty much. Rocketry isn't as fundamentally difficult as many people make out, and a lot of the stagnation in spaceflight is due to bureaucracy and excess risk aversion, not fundamentals. SpaceX had succeeded due not to being absurdly better at engineering, though they are good, but at striking the right balance of innovation, pragmatism, and risk.
They're apparently also used in the Soyuz launch escape system.