You've got it all wrong! It was actually an incredibly genius move, as the writers knew that after 7 seasons of twists, turns and surprises, the audience wouldn't really be phased by any characters death anymore. We'd become so accustomed to sudden character deaths that watching GoT became the literal incarnation of "expect the unexpected" and you can't shock people who are just waiting for it to happen. So what did the showrunners do? They did the only thing nobody expected, assassinated the only target they knew would still get a reaction out of people after all this time - they killed off the show itself.