Archaeology doesn’t really confirm Alexander’s existence in the way you think it does, Patriarchy. Buildings and cities named after him are not evidence he personally founded them, especially when archaeological dating suggests many of them were later. Suggest you read a little on how fame and biography worked in the ancient world if you think Alexander’s later biographers were setting out dry factual statements.
It’s surprising you don’t know more about the historical evidence for Alexander given your clear interest in provable historicity, because he is always trotted out as an example of how we often don’t have the kind of evidence that a naive approach to history would suggest we do. The point isn’t that Alexander didn’t exist, he almost certainly did; the point is that we typically don’t have the kind of ‘evidence’ we’d expect to have from a 21st-century perspective. So Alexander is a good basic example of how we can use references to eyewitness accounts in later writings, even though those primary texts themselves no longer exist, or how we can use the example of someone from another culture mentioning that “the king died” and know from our more detailed knowledge of that culture that he’s the king they’re referring to.
You can say the same about Jesus, right?
In the sense of main accounts that specifically reference contemporary eyewitness accounts, yes, that would be the synoptic gospels. That is literally how the author of Luke starts, the Greek word used is even typically translated as “eyewitnesses”. In a Biblical scholarship context (I know you think this doesn’t exist either, but bear with me!), the gospels and Acts were written around the time the earliest members of the early church were starting to die off and the community realised they were going to have to start writing stuff down now.
We have about as much evidence of Jesus’s existence as we’d expect to have of an (at the time) fairly minor religious figure in a Roman provincial backwater, which is: not much directly, increasingly more about the movement that started around him in the decades immediately following his death. We have barely any more evidence that Pilate existed (he probably did though).
I really don’t care what you believe, though. I’m not interested in trying to convince you of the historicity of Jesus, it’s no skin off my nose one way or the other. But you’re wrong about some of the factual claims you’re making, and you know substantially less about historical Biblical scholarship than you believe you do.