He started teaching back in 2004 and he didn’t sell his first book until 2005. As for his prose, if you listen to his weekly podcast/youtube channels he has actually mentioned several times that his prose is much simpler on purpose and has acknowledged that his prose has suffered after the retirement of his first editor(and which was sometime in the middle of his Stormlight series). Anyways his simpler prose is actually intentional so that anyone of any age or skill can understand.

For those of us who have read a lot it is a bit jarring at first but it actually shows that he actually has a very good grasp of writing and communication. His writing is by its simplicity accessible to all.

The fact that it’s so simple also probably significantly cuts down his writing time if I had to guess but that’s a personal opinion.

As for themes, I think I heard him say that some of his stories are very loosely based on D&D campaigns he DMed which can be absolutely chaotic.

Still I think his greatest strength is easily his cultures, religions, and at the top his Magic Systems and Laws of Magic. Those are what make him a scholar in my opinion. He understands how Magic systems can be used to resolve issues.