I know multiple-payload launches are routine these days, and everyone seems to have their own reignitable kick-stage. But who were the first to start doing that?
This is similar to this question, but that was answered with the first attempt at a multiple-payload launch, which was a failure. Who was the first to do it routinely as part of their business model? I know the Ariane V was designed specifically for that, but I don't know that it was the first.