Not crazy, just ignorant.
People in the same party agree on more than 90% of issues, while people in the other party disagree with them about 90% of issues. There's a whole structure of position forming that is highly dependent on ideology and tends to flow down from thought leaders. Just for example, Trump literally doesn't even know what the Federal Reserve does, but you know he's going to favor tighter money because that's what the right-wing intellectual apparatus wants. Clinton could probably briefly explain arguments for different approaches to monetary policy, but those will be things she remembers liberal economic advisers explaining to her, and we can make a very good guess about what her ultimate positions (and thus the type of person she'll appoint to set it) will be.