But it does prove that guessing btc private keys can be successful.
The only thing that your post proves is that either you are too confused about what happened (if we give you the benefit of the doubt), or ....
You also didn't need to move the coins to prove you have "found" the key, you could sign a message from the address that has the balance and post it here as proof...
It’s possible that the way he coded his program was to start at private key 0. Which is low entropy. And these have been sweeped years ago but someone maybe sent some funds to one address which has a low entropy key but the fee to sweep it is higher than the value of the bitcoins inside, since fees are high right now.
It is a possibility but a small one since usually there are many "scripts" written to watch these keys for any funds and steal them right away. Which means it is nearly impossible to see any of them having any confirmed balance for long.