You can't possibly prove that you're the original owner of this account and you can't possibly prove that your account was ever hacked. You might have dug your hole just a tad too deep here.
You really like holes and enjoy trapping people. Pathetic.
Or you could read and find out that legendster said himself that his e-mail and his private keys have been compromised.
Ok pointing game !
I already easily noted that legendster had very bad OpSec practices overall, but that doesn't mean he is high risk to trade with and worth tearing his account apart. Its common to save data online and forget about it if you don't use the same medium the most.
Don't you think you are going full cat gang mode here ?
About, his comprised email and private keys - He could still have access to his old telegram handle which he has posted here many times. So, it could still prove the account ownership.