I don't know what to say. Something started so beautifully desrerve the same beautiful closure as well.
Whenever writer writes a story, he shapes characters, thier behavioural traits, their mannerisms in certian way. All characters collide each other in certain situations, all characters have some back stories. And writer gives proper closure to all the back stories of each character. Thats how the novel comes into existence.
I don't know how they write tv series, but its similar to writing a novel in my opinion. Here, I guess writers haven't developed the entire story. But many people interfered and ruined it in totality.