The man regularly made transactions from one of his wallets to another. The scammers took advantage of this. They picked a similar wallet, which differed only in the last characters from the potential victim's wallet, and sent a small amount from it to one of the man's wallets. After that, they began to wait.
The amount was so insignificant that the man did not even pay attention to it. And then, after some time, he needed to send funds as usual from one of his wallets to another. As always, he copied the address from the last received transaction, the first letters of which he knew by heart, and made the payment.
The money went to the scammers. When the man checked the addresses of the wallets, he realized what had happened. It turned out that someone sent him funds from a very similar wallet. He received less than $1, and in return sent about $2 million.
This type of fraud is quite rare, but, nevertheless, due to carelessness, you can fall for it. You should always carefully check the wallet address, down to the last character, and remember that even someone else's wallet may be in your clipboard. We wrote about this new virus earlier.