Twain has survived his celebrity, as will Hemingway, and for the same reason: They wrote wonderful books. but both writers have been admitted to the canon despite the off-putting aroma of publicity that surrounds them.
Dose it mean that they were accepted by law (their works were excellent) despite the fact that publicity just was annoying to them?
First the author of that quotation makes an assumption, or an implicit proposition: celebrity is bad. We can agree or disagree with that idea, but for the passage to make sense, we must understand that the author believes this.
They have been admitted to the canon
Canon has a variety of related meanings. The one being used here is
3.c. a sanctioned or accepted group or body of related works
https://www.merriam-webster.com/dictionary/canon
In other words, Twain and Hemingway (or really, the works of Twain and Hemingway) are now included in the collection of books that people generally consider to be important, or great literature.
despite the off-putting aroma of publicity that surrounds them
As mentioned above, the author believes that celebrity is bad. Despite being afflicted with celebrity, the authors (really, their books) have been canonized.
The canon is the set of books each new generation of readers is expected to read at some point if they wish to consider themselves educated. The list is somewhere in between de facto and de jure. These authors are taught in schools and then later included on syllabuses at university.
Those two authors continue to be regarded as worthy of such status despite the fact that they were very much in the public eye while alive. Notoriety whether because of personal scandals or unpopular political views can keep an author out of the canon or can cause an author once in the canon to fall out of favor. And popularity itself can cause an author to be dismissed by some pundits as a "lightweight".
