Money is no issue now for him, but it must suck to get your work spoiled on the TV show, because this is what is going to happen, at least certain very important plot points of the saga. This has already happened, see: "hold the door".
GRRM also thought there would be more from his books in the show and he had a much bigger cushion of time. Not that it would have mattered anyway, which is why I don't really get all of the complaining. At best, he'd only be one book behind, instead of two, and the ending would always be revealed in the show first.
Its very much his fault though, GRRM has let the fame/money consume him whereas other "celebrity" authors like Rowling and Stephen King remain steadfast have avoided that fate. Its his own legacy that's being tarnished, he will always be that author who let the material world overcome his artistic sensibilities, and if he actually doesn't finish the books? That would be truly ironic for a guy that obsesses over legacy and pines for his works to be the next entry into the fantasy literary canon like Tolkein.
He could have gotten them out quicker if he gave more of a shit. He's one of the slowest writers in recorded history and types just with his index fingers IIRC, on ancient technology.
He spent a couple of years doing constant appearances and press shit for the show as well. TWoW just hasn't been a priority for him until the last few years.
He's always been a slow writer. He makes it worse for himself with the DOS machine, only writing at home, typing with
one finger, working only on individual POVs, but I think it's petty to get mad at a guy who wants to go to cons and bask in adulation, to travel and enjoy his success. People get pissed off at him for watching football, for goodness' sake. Writing is a job, and not a particularly fun one; when you get asked to come in on Sunday, you get pissed off, too. Half your fanbase worships you, the other half think you're a lazy, fat fuck.