He's certainly riding on his previous success, but only a tiny bit, if you look at the orders of magnitude increase in his sales.

How did many thousands of new readers find him and decide to buy his books almost without doing any promotion? Through much lower cost of books, instant delivery, easy discovery through search and auto recommendations. And now he has more time to produce more. Accelerating sales!

The 1,000 true fans analogy doesn't hold for him at all. He has at least 10,000 fans and that number is going up fast.