Where on Earth do you get the idea that monuments to pharaohs were not built within their lifetime?

Consider the Boy Pharaoh, Tutankhamen. He was dead at the age of 17, before the completion of his tomb. And thanks to repeated grave robberies, his tomb had to be repaired and refortified on subsequent occasions. His elderly successor and family advisor, Ay, was buried who died four years after his own ascension to the throne, effectively swapped Tutankhamen's intended tomb and claimed it as his own, but never lived long enough to see it completed.

Numerous unfinished or partially completed tombs dot the Valley of Kings. And even the Great Pyramids have several chambers that were started but never filled out before the builders were retasked to the next Pharaoh in line.

It also misses my point.

The standards by which we hold "historical Jesus" would disqualify a litany of other historical figures of antiquity, as the bulk of our knowledge comes from reprints of reprints of surviving accounts of other accounts which are themselves often politicized documents intended to score contemporary points.

The Hellenistic Era might as well not exist, for all the first party accounts of the era that survive. Herodotus was dead before Darius the Great was even born, and yet his histories are fundamental to understanding the Achaemenid Empire during his reign. The only surviving copy is dated fifty years after the events it claims to document. That's roughly as reliable as The Gospel of Mark, which is dated some 30 to 80 years after the death of its primary subject matter.

If you want to hold historical figures to equal standing, you're going to write off everyone from Archidamus II to Cyrus I. Obliterating huge swaths of history with a single pen stroke, because Herodotus is an unreliable narrator.