That would be success in art but failing in life, by the quote definition, I infer he’s equating success in life with your minimum quality of life indicators being as high as posible, if I got it right.

That's how I read it also.

Take for example Kurt Cobain (whatever you think of him and his music). He had major success in music, but his life was a disaster and not something I'd hope for a loved one.

I do agree that it seems like the best art is created by "tortured artists".

Do you think he'd be ok with the opposite - a bland, contained and long life?

What is life for? There are fundamental questions here and I don't think the answers are obvious as you seem to think.

Tortured artists have produced some great work, true.

J. S. Bach had some hardships in his life, but he wasn't tortured.

J. R. R. Tolkien, similarly, was not tortured.

da Vinci's life doesn't seem to have been horrible either.

I think they stand as strong counterexamples to the idea that tortured artists make the best art.

Tolkien wasn't tortured, but he fought in WWI.

I guess people (particularly Tom Shippey, IIRC) do argue that's a lot of what made his work what it is. I tend to forget about that part of his history.

Certainly it would have been a traumatic experience.

Definitely a relevant point. Thanks for mentioning it.

Is their art good because they are tortured, or despite being tortured? People tend to assume the former, but it's unclear why the latter cannot be true.