Sorry to hear that you got ripped.
Firstly, I'm not sure if you have seen Coolcryptovator's tag on him:
This user selling multiple account verified with KYC. According to admin post :
https://bitcointalk.org/index.php?topic=1785577.0 , "Accounts on sites that require KYC such as bank accounts, PayPal, etc. are assumed to be hacked unless you explain why they're not hacked." So this tag will remain if this user unable to provide appropriate evidence with explanation why account's are not hacked on reference thread. See reference link for more details.
As he says you should never trust KYC verified account sellers. You simply don't know how they obtained the accounts or how they are verified, and most likely they are fraudulent. If Binance finds out that you are using someone else's account with different KYC info, you are screwed and you may never get your funds back. The original account owner may also claim at any time that his account was hacked, and you could also lose funds as a result.
It's not something that you want to be involved with if you want to build an exchange service.
Secondly, reputation outside of the forum is completely irrelevant given the fact that they can be easily manipulated. Also, escrow should have been used given the high amount that was at stake here.