Yes, IIRC everyone at Amazon has a hardware security key (which is more secure than the standard mobile app TOTP most of us use everywhere online).
Is it though? The "wrench theory" applies here. It's not unthinkable that an employee was stalked on social media and had their key stolen.
More secure != perfectly secure.
The main security benefit is unphishability. With yubikey/webauth crypto is used so you can't give the code to the wrong website. Phishing is a pretty major cause of account hacks generally, so pragmatically that is a very big win.
With a Yubikey, you need to use your password to log in to your computer, and then need to auth using Yubikey.
With OTP app, you need to use your password to log into your computer, passcode for phone, and then auth.
In both cases, it's something you know, and something you have. You could argue that the app based is a bit more secure in that you need two passwords. On the flipside, if your phone gets pwned, someone can access completely remote.
Everything is a tradeoff.
I don't know which protocols they use (obviously), but if they use WebAuthn, everything is public-key signatures. Even if you leak everything from the server, public keys buy you nothing.
Luckily iirc from a conversation with a senior Twitch engineer the Tax information backend has been migrated to Amazon. So hopefully that did not leak... Because that would be full legal name and addresses of a ton of streamers that likely have stalkers.
It'd be strange if they don't have two factor auth, of course, but it's just as strange to have this large of a hack.
I think if it is a simple case of an employee account takeover, then the attack would "work" to some extent at any company. Larger companies typically have strict data access requirements, though. Good luck finding the few employees who have raw access to Google password hashes, for example. And even more luck knowing how to get that data if you do.