Used the app store to search for apps instead of going straight to the developer's site and verifying the download.
Downloaded a fake app even though Trezor doesn't even have an iOS app.
Didn't read all the reviews calling it a scam.
Blindly entered his seed phrase in to the fake app.
And now, according to the article, he blames Apple for "betraying his trust" and says they shouldn't be allowed to "get away with this".

It always amazes me how someone can hold hundreds of thousands of dollars worth of bitcoin and yet still be so monumentally uninformed. He had to do literally
everything wrong to fall for this scam. The slightest bit of knowledge or due diligence regarding any one of these steps and he wouldn't have fallen for this. But no, it's Apple's fault.

So what OS must we use ?
A reputable Linux distro such as Ubuntu.
More importantly than what OS you use is to not just download random pieces of software you stumble across like this user did. If you want to download a crypto wallet or app, then make sure it is open source, visit the developer's site or GitHub directly, and verify your download's PGP signature.