It makes zero sense
Ideologies don't have to make sense, see: Communism.
Big pharma has no power on its own, it's the banker class who sign what big pharma does and doesn't do. And the banker class doesn't really give a fig about the working class, to put it mildly. In fact, they would rather us be dead, and only begrudgingly accept our lives as a necessary evil because they're fucked in the head.
The banker class also has been recorded to want only 500000000 people in the world. We're heading towards 9 billion sometime soon.
Oh golly, if only there was a way to kill 7 billion plus people without any fear of retaliation. Almost like people would, out of their own volition, accept a "treatment" that would actually be poison in order to have their freedoms back.