I misunderstood it for so long because I took it quite literally. When you present The Trolley Problem at its most basic level, nearly everyone will say that the most moral thing to do is pull the lever and redirect it to the single person.
But then I was watching a TV show that presented it in another way. Imagine you have five people about to die from various illnesses, but that each of them can be saved by an organ transplant, and each one needs a different organ. Would it be immoral to sacrifice someone else's life against their will to harvest their organs to save the other five? Nearly everyone would likely say yes, it's incredibly immoral.
But it's really the Trolley Problem. You do nothing, five people die. You take an action, you sacrifice someone against their will to save the original five.
Perhaps when you sacrifice someone, you are the murderer, the knife wielder, but with the trolley problem, the trolley is the murderer.
But can moral principles be a numbers game? I don't think so. Otherwise a serial killer who murders 9 people could claim higher moral ground than a killer with 10 kills to his name.