they are not crazy they are just very energetic dogs and want outlets for all this energy. if their owners to do exercise them properly, nurture them the right diet, and supply them with decent interactive toys yes they may appear to be crazy because their energy have no outlet.
Each dog has its own personality. Try walking yours more. Itll love you forever. :)
Answers: Google 'Cocker Rage'. That should answer your question. They were extremely overbred in recent history near no regard to temperament or suitability. Some of them have, literally, defective brain chemistry major them to 'snap' and exhibit severe aggression, sometimes with no prior history of aggression at all.