In "Hunter: The Strange and Savage Life of Hunter S. Thompson", it's made very clear that Hunter did _not_ write while he was sober. An excerpt of his daily schedule -
9:00(pm) starts snorting cocaine seriously
10:00 drops acid
11:00 Chartreuse, cocaine, grass
11:30 cocaine, etc, etc.
12:00 midnight, Hunter S. Thompson is ready to write
The OP was talking about "William Faulkner, Eugene O'Neill, Ernest Hemingway and John Steinbeck"... "what about Hunter S. Thompson?" isn't really a good argument. He's not considered a great writer in the grand scheme of things, I think he's better known for being a drug addict.
The idea, since it appears to have been lost on you, is that there's a long history of great writers (like Thompson) using drugs while they created. The Thompson quote is one of many, I think that's the part you may be misunderstanding. Truthfully, I'm surprised that a single Forbes article which quotes a "Michelle Stansbury, PR expert and founder of Little Penguin PR" is enough to have convinced you otherwise.
https://www.forbes.com/sites/henrydevries/2018/12/11/ernest-...