Nobody knows for sure how Dale Carnegie died and whether it was a natural death or a suicide. But, it seems very logical that the news of his suicide may not be completely wrong because of his contradictory life and frequent failures. The person who is regarded as a messiah of human relations by the entire world failed measerably in maintaining basic human relations in his own life. He was married twice and both of his marriages had failed, ending in bitter divoce. And if he committed suicide, his company Dale Carnegie & Associates would never admit that because the company can not afford to loose millions of dollars by accepting the fact that Dale Carnegie was a fake preacher.
His second marriage lasted until his death. He died of Lymphoma. Those are facts. The conspiracy theory is bs