The thing is that here the scammer has the mine trap setup and ready to blow. I doubt that there is anyone who would be able to notice it or think that the account was compromised and freeze the deal. Unfortunately, it might happen to anybody.
That's where all gone wrong. It was like the escrow was talking to the same person but it was not. The person behind the account was changed. This could happen to anybody.
I refuse to believe that, otherwise no trades can ever take place anymore. It is possible for an escrow to (learn from this and) impose escrow rules that can prevent this.
Whoever gone through this experience (by watching or being in discussion or just a quick read) I am pretty much confirm that from now on they will check account logs. I will ask from a bitcoin signed address for sure in every conversation especially when the time to make the trade.
When the terms are changed after money has been sent to the escrow address, the escrow agent needs to be sure that everyone is on the same page. MJ should have delayed releasing the money. This might be inconvenient for the parties involved, but it is the escrow agent's job to ensure a safe transaction.
I think I already said, nothing was alarming as the instructions were coming from the same account.