It depends on the viewpoint!
Yes, creative people "appear" crazy to those who don't understand their creativity. That does not, in fact, mean that they are crazy. Crazy is typically associated with delusion -- a break with reality. Creative people merely make a new "reality." The value of that creation frequently increases with the ties that creativity has with the common reality we share. Otherwise, even the most avant-garde audience might not "get it." Certain "rules" apply that an artist usually shouldn't break--like no one element of their "art" overwhelming the others. Until I understood this, Picasso seemed "crazy."
Non-creative people are perhaps limited in their exposure, interests and thus understanding.
It's a matter of "unreality." What a creative person does may seem "unreal" or not "of reality" or not "reasonable" to someone else. Someone else might consider it entirely real.
That "unreality" can be handled with a little TLC -- kindness and affection from the creative person and communication about what they've done that seems so unreal. This can make it more real to some. Others may refuse to hear something outside their realm of experience.