Smarter people than you have accepted theism and religion why do you think you are right? Do you think you're smarter than they were?
It is true that smarter people than I and many other atheists have accepted theism and religion but so what? Smarter people than you have rejected your brand of theism and your brand of religion in favor of some other type of theism and religion. Smarter people than you have rejected theism and religion entirely, leading an entirely atheistic and irreligious life. Do you think you're better or smarter than they were? Is this a reason for you to drop your theism and religion? Of course not.
This question is designed to suggest that, if smarter people than I have accepted theism and religion while I have rejected both, then perhaps I shouldn't be so arrogant by continuing to be an atheist. Perhaps I should reconsider, giving theism and religion another try, yes? The question can be turned right around, as I have pointed out: why don't theists and religionists reconsider and become atheists given the existence of highly intelligent irreligious atheists?
The reversal of this question is arguably stronger, in fact, since we know that people in the past didn't know as much as we do today, while today there is a strong correlation between greater education and increased rates of atheism. Great scientists and philosophers in the past believed a number of things which people today recognize as false; they didn't believe things which people today recognize as true. If you're going to rely on the opinions of anyone, it's better to look to people of the 20th and 21st centuries, not 16th or 17th centuries.
Ultimately, though, you shouldn't rely on people's opinions in this way at all. The reason why these arguments don't really work, no matter which way they are directed, is simple: the mere fact that someone smarter than us accepts or rejects some belief is not by itself a good enough reason to do the same. The idea that it might be is a straightforward example of a fallacious argument from authority: it is assumed that a smart person is an authority on what they believe, and hence we should accept for ourselves whatever they have accepted. The error of such thinking should be obvious and hardly anyone agrees with such an argument when it is put so bluntly.
There is a secondary question in the above which also merits attention: why do I think I am right? This is based upon a slight misunderstanding of what atheism is about. Atheism is not an assertion about which a person can be right or wrong. Some people mistakenly believe that being an atheist entails asserting that "no god exists," and thus is something a person can be right or wrong about. In truth, atheism is simply the absence of belief in any gods, rendering the description of right or wrong inappropriate.
More accurate and appropriate would be: why do I think that my position is reasonable? This is appropriate because disbelief in gods can be reasonable or unreasonable; indeed, the atheism of some people can be reasonable while the atheism of others can be unreasonable. Atheism cannot be inherently reasonable; if it is reasonable, it is because of the reasons a person has for being an atheist. The same can also be true for theists and religionists. For myself, I consider my atheism reasonable because I fail to find any sound, rational basis upon which theism can stand.
So long as I can't find any good reasons to bother believing in any gods, then a reasonable theism is impossible for me; moreover, I find myself unable to adopt a belief which I consciously know is unreasonable. Therefore, it is currently impossible for me to be a theist and, therefore, I think atheism is the most reasonable position I can possibly have right now.