That Lexus is an EV.

Engineering Explained did a really good video about this: https://www.youtube.com/watch?v=agMrewRJTow

To save going through that whole video for the answer: they have redundant power supplies (3 batteries total) and redundant actuator motors.

But the fact is if there is a bad enough electrical/wiring fault, especially as the car gets older, you are toast and you have no steering.

Of course the same thing can happen with mechanical steering (eg a broken linkage) it comes down to the quality of the design and build.

The whole design will be such that a single electrical fault can't make it fail. It probably has at least 3 channels.

Probably won't even allow you to start the car if one of them is faulty.

This kind of thing will almost certainly be designed to comply with ISO 26262.

I've had the power steering cut out on me in a traditional ICE car, you're pretty much hosed in that situation, too, as far as steering is concerned.