I am quite sure it is not the first show in history where that is the case!
Also, I think it may have succeeded in the early days because of them. Hear me out! Stop booing and throwing things! 
I think this because the ASoIaF novels were intentionally challenging to film. GRRM, by his own account, wrote something he thought could never be filmed, because there’d never be the budget or will. I feel like a lot of showrunners, especially experienced ones, would have realized this and not even tried to film them “as they were”. They’d have made vast cut and fundamental changes, which D&D did not do in the first seasons, because they’d have seen the issues. They’d also probably have cut and compressed a bunch of the characters, and changed them in ways beyond making them all about two-three years older. Further, I suspect most showrunners would have not used as much of GRRM’s dialogue, because they’d have “known better” than to do that.
So my thesis is that their naivete and the fact that they had no idea what they were doing caused them to both “go for it” and try for something bigger than most people would have, and to retain vastly more of GRRM’s dialogue and plot lines than other showrunners would have, simply because they didn’t have confidence in their own. The first two-three seasons run astonishingly close to the books and benefit from it.
Had another showrunner handled the same material, I suspect they would have produced something far more mainstream and less bizarre, which captured the public imagination less, and was less true to the (very popular) books.
Of course, the exact same traits are what fucked them in the end - they understood the material and characters significantly less well than the actual actors, they couldn’t write much good dialogue without GRRM there to help them (though “chaos is a ladder” is pretty immortal), and without the solid structure of GRRM’s plot, which they lost actually due to GRRM, but still, they proved that they were not great plotters. Still, I suspect a GoT by a more “competent” or experienced showrunner would have been a lot less true to the books, and probably less exciting overall.