Sanddidit.
Most cultures speak about a big boat filled with animals? I doubt it. To pick a big one, Classical Greek and Roman mythology doesn't mention a world flood. The Norse and their relatives don't have any such story, either.
Concerning Egyptian records, how many kings and cities have been swept away by the desert sands?
We have pretty good written records from the Egyptians going back well past when the flood supposedly happened. There is no break in the Egyptian chronology.
Your asking me to disprove a negative. (i.e. Why is something not there?) I'm not taking the bait.
I can get the same result by asking you to explain why those records still exist. Egyptian writings go back to about 4500 BC. Papyrus was invented around 3000 BC. Papyrus doesn't respond well to water, and yet we have many, many Papyrus writings from before the date that the flood was supposed to have happened. Can you explain their survival?
Most likely, the Biblical flood story comes from around 2200 BC, when Sumerian priests invented mythic science fiction, and wrote a story about the flooding of the earth involving many gods and a pious king Ziusdra. Around 1800 BC, the Bablyonians adapt and expand the flood story in their Epic of Gilgamesh involving the pious king Atrahasis. Around 500 BCE, Hebrew priests in Babylonia take the regionally popular flood story, reduce the gods to one, and demote the king to a commoner named Noah.