Why would the apostles spread the word of Jesus Christ if false?

People would say it is because they were "crazy" or "brainwashed" or "random happenings". That is the excuse being used all the time. If it's not able to be proven with tests it's "a crazy delusion". Go figure huh? I guess that is a better explanation. I don't think it is but aw well. I does not make sense to me either why all of those people would lie and be brutally murdered for nonsense.