Your own words betray your claim of rationality, unless you have definitive proof that there were no geysers. Othewise, geysers remain a possiblity, regardless how remote that possibility may seem.
There is absolutely no evidence whatsoever of cold water geysers being discovered on the Giza plateau.
But with your fantasy brain in overdrive, now anything is a possibility, no matter how remote.
Let's add in some remote possibilities for building the pyramids which you can mull over along with geysers.
What about the remote but possible idea of hundreds of desert rats powering treadmills?
What about the remote but possible idea of super large kites made of papyrus?
What about the remote but possible idea of nuclear powered wands?
And you wonder why I use the term "crackpot."