There was a time when the newspapers said that only twelve men understood the theory of relativity. On the other hand, I think it is safe to say that no one understands quantum mechanics.
Nobody knows how it can be like that.
The mathematical formalism of quantum mechanics, though refined and generalized in the intervening decades, has never been seriously challenged either theoretically or experimentally and remains as firmly established today as it was in the 1930's. And yet over the entire period since the original development of quantum mechanics there has been controversy surrounding its interpretation. The questions of the meaning of the mathematics and of the underlying reality behind the laws and procedures of quantum mechanics have been a battlefield for five decades, and no truce is yet in sight. The controversy has, in fact, recently been intensified. CFD is actually a rather weak assumption and is often employed by practicing physicists in investigating and discussing quantum systems.