They don't all know, at least the whole plan. I'm not sure what distinction you're making here as to how morally corrupt the Elves as a whole race are when you say they're evil, if at all.
Most of them aren't aware of the full intentions and depravity of Potimas. They're all arrogant, they believe they're superior to all other races. They're skilled at deception, which is why gaslighting Oka is both easy and natural to them.
But most of them believe that they're saving the world and everyone in it from the System. They follow Potimas because they actually think he's going to lead them to that goal (of course, he isn't). Even though they despise the 'lesser races', they still believe they're saving them too.
That's relevant to the context of sacrificial pawns. As I said, they're loyal to Potimas because they don't really know. And so they don't know they're pawns to be sacrificed.
I think it's explained explicitly earlier or later in the story, I can't exactly remember when. But I'm certain it was, because this was something I was curious about years ago. But even without that, think about it. If the Elves are all evil, and all of them know Potimas's plans. Why would they follow him and willingly let him treat them like toilet paper to wipe up shit then get flushed away? They're brainwashed, not mind-controlled.
