Too popular too fast?
....
Considering he's been writing since the 70's, and that his "fame" came mostly after 2000, I wouldn't say that. Have you even read his sci fi and other books? Heck, even his TV shows scripts are interesting.
And I think every writer would be incredibly honoured and high about his series being turned into a movie or TV show. Seriously. That means something, that something you created with your own brain and imagined from the get go to be put on screen, to suddenly see his own character appear on screen and think "wow, it's me who did that". Not to mention that Martin is quite invested in this too, since he's going to write one episode per season.