You should say "The people are crazy". 'People' is plural form of a person. As a piece of information to clarify the same, here's quote from Apple's publicity campaign: "The people who are crazy enough to think that they can change the world are the ones who do". read more
2. They are too foolish to be scared. When crazy people set goals for themselves, they aren’t concerned with the “what if” possibility of failure. read more