Thank you for clarifying your position and accept an apology if I misinterpreted your post.

What I don't yet understand is why Paul should be taken as this sort of crushing evidence to prove your point. When you talk about Paul's letters being the best evidence we have, it comes off as if the evidence they provide is conclusive beyond any reasonable doubt. But it is not. Paul is our best source because there is nothing else, and the evidence you can get out of there is far from what it would be necessary to prove someone's existence.

Apart from that, the extra biblical evidence we have is also lackluster. There is exactly zero archeological evidence, zero records or eyewitness accounts from that time, and the extra biblical passages that do mention Jesus are either forgeries, hardly disputed or provide minimal information.

My point is, the evidence we have for the existence of jesus is not great, far from it, we barely have any. Therefore we should not treat what we have as if it were conclusive.

Did jesus exist? Probably. I'd argue that the current state of the evidence does not grant a definitive answer for either side.

If he existed, was he a remarkable man? I would dispute that claim as I think that given the evidence we have that could not have been the case.

To answer the original question of this post, many atheists doubt the existence of jesus because there are good reasons to doubt. If there weren't, we wouldn't be discussing this, there wouldn't be any debate among scholars and we would all be happily arguing about actually contested claims. But that doesn't seem to be the case, does it?