Mindlessly clicking through OK buttons is end-user negligence, not fraud. Your brother presumably had multiple opportunities to notice something was not okay before completely signing off on it. It's tantamount to signing a contract without so much as even glancing through the terms, then turning around saying you never meant to sign it.
Fraud protection does not absolve someone from being a responsible adult.
PayPal's "redirect the user through our services" flows provide more uniformity than some random site with a hosted-- or even baked-into-the-shopping-cart-- credit card form-- but I wouldn't say it's uniform enough that people would be able to reliably identify something outside the norm.
Just think of currency-- could you spot a decent quality counterfeit? Particularly if you're dealing with a more edge-case design that you don't encounter every day (say, a Series 1934 $50 note)?
I hate to say this, but there will always be loopholes as long as scamming js lucrative enough.
When it's easily verifiable that actual fraud has taken place I would say yes. It would've taken them literally 5 minutes of their time to investigate by going to the website, seeing it presents itself as a retail furniture store, and to go through the checkout process and seeing that it ends up at a form for a personal transfer, and that no goods ever end up being delivered, all of which clearly indicate the transaction is 100% intended to be fraudulent by the supposed seller.
Fraud management is hard. Most actors in the domain are also jerks, but that's orthogonal to it being hard I think.
He had to do a chargeback with his credit card company and got his money back that way, but of course PayPal banned his account in response.