So what OS must we use ?
The weakest link in the software is the user.
There are thousands of windows users who haven't got "hacked" and tricked into downloading malware and there are also thousands of user who have downloaded crap even on iOS on on other Linux systems, people should understand that Linux is not some kind of bulletproof solution to everything and once you got that on your computer you're completely safe.
The exact thing happened to the victim he believed nothing could go wrong and he went whistling through all the steps o_e_l_e_o mentioned and probably a lot more users did the same but they've kept quiet about their loss.
I dont believe that users got scammed due to downloading fake app directly from App Store. All apps passes tons of moderation before getting into App Store. Despite Google Play Store, which is full of fake and scam apps. It is mentioned that he had downloaded an app from App Store. That is a lie, there is no such app there and never was. Just another case of a user that does not care much about his security, as he "downloaded an app to check his balance".
So you claim that all those people lie and you know better?
Kristyna Mazankova, a spokeswoman for Trezor, said the company has been notifying Apple and Google for years about fake apps posing as a Trezor product to scam its customers. Trezor has never had a mobile app, though the company is working on one. She said the process of reporting the apps is “painful” and that representatives of Apple and Google haven’t been in contact.
Mazankova said Trezor notified Apple about a copycat app on Feb 1. Apple removed the app on Feb. 3, but it appeared again days later, according to Christodoulou, before it was removed again.
The fake Trezor app got through the app store through a bait-and-switch, according to Apple. Though it was called Trezor and used the Trezor logo and colors, it represented itself as a “cryptography” app that would encrypt iPhone files and store passwords, according to Apple. The developer of the fake Trezor app told Apple’s review team it “is not involved in any cryptocurrency.” Apple approved the app and it appeared in the App Store on Jan. 22, according to mobile analytics firm Sensor Tower.