>>279694613
The point is that alchemists make alchemy their whole identity and they become so reliant on it they don't even realize sacrificing it is an option. It took someone who was willing to humble himself to see the truth, that alchemy is just a tool that doesn't let you live life any better than if you didn't have it. Alchemy caused them to get into the situation they were in, so to get out of it, he gives up alchemy. It's equivalent exchange and this is really not very hard to understand since they spell it out for you in this scene