The reason is quotes like this:
"Religion is simply an ideal. It is an ideal force that tends to free the human being from material bonds. I do not believe that matter and energy are interchangeable, any more than are the body and soul. There is just so much matter in the universe and it cannot be destroyed. As I see life on this planet, there is no individuality. It may sound ridiculous to say so, but I believe each person is but a wave passing through space, ever-changing from minute to minute as it travels along, finally, some day, just becoming dissolved."This quote in particular is used to claim that Tesla did not believe in religion, the soul, or Einsteins physics. None of this is true.
"Ideal" can mean many things, such as "a conception of something in its perfection" or "an ultimate object or aim of endeavor, especially one of high or noble character," but even in its most negative connotation, which I think Tesla was using, it means "something that exists only in the imagination." This is absolutely true. Religion exists only in the mind. However, that does not mean that God also exists only in the imagination. It does not mean that Tesla does not believe in God. In addition, just because religion only exists in the mind, it does not mean that religion is bad. Tesla speaks of religion as a positive, liberating force, "[freeing] the human being from material bonds."
Another quote, which illustrates Tesla's spirituality, is this one, in his autobiography:
"The gift of mental power comes from God, Divine Being, and if we concentrate our minds on that truth, we become in tune with this great power. My Mother had taught me to seek all truth in the Bible; therefore I devoted the next few months to the study of this work."Tesla attributes the gift of mental prowess to God and not only viewed the Bible as the source of all truth, but apparently devoted months at a time to its study. And this one:
"Peace can only come as a natural consequence of universal enlightenment and merging of races, and we are still far from this blissful realization, because few indeed, will admit the reality that "God made man in His image" in which case all earth men are alike. There is in fact but one race, of many colors. Christ is but one person, yet he is of all people, so why do some people think themselves better than some other people?"So not only did Tesla believe that peace could only come through the realization of the doctrine that we are all alike, but he derived this truth from Christian doctrine. In other words, he used Christian doctrine as a way to say that we all equal and no one is better than any other person. As with most things involving Tesla, we need more of that.