It's my understanding that the drug companies themselves, operating outside the US, are the ones making these drugs unavailable for death penalty use. They are engaging in a straightforward boycott.
Corporations are amoral. The activists found a weak point in the death penalty system -- namely, the companies which make the drugs (which is a small market to start with) and are terrified of even the remotest smidgen of public criticism.
It really is creative activists trying things against the will of the people in those states that support capital punishment. I've got a complicated relationship with the death penalty, but that aside I recognize that the only way to change it is through the institutions we have which are empowered to make those changes.