After all, you never could fault Jordan's writing speed or release pace, just the way he lost control of the plot. And I really don't believe that Jordan milked the series for commercial purposes - frankly, by the time of book six, he had made plenty of money already. Besides, I think he wanted to be done so he could move on to something else, whether an entirely different project or some side-project set in Seanchan or wherever, as was suggested at some point iirc. He just literally lost control - introduced too many side plots that he just couldn't bring himself to cut but also didn't manage to tie up fast enough. Perhaps a stricter editor might have helped - one who wasn't his wife - though any author who's had that much success already is bound to get plenty of leeway from their editor.

In Martin's case, he created expectations he couldn't live up to, both in terms of the writing and in terms of the release pace, with those three strong opening books released in such short succession. Then he got stuck while also wanting to dial back how much of his time he spent on aSoIaF... and the more impatient fans became, the less motivated he got, I guess. That being said, both his books and the TV series based on them did have very strong starts and were hugely influential for the wider genre, so you can hardly consider them failures... he's just not as strong a finisher as he is a starter, clearly.