Whelp episode 6 was shown for an hour in spain Don't click that link unless you want to see mega spoilers.
https://www.reddit.com/r/freefolk/co...for/?limit=500
Pretty much confirms the night king has been toying with Sam Jon and Bran for years, using them as tools in his master plan he takes down Viserion so easily.
The night king has been shown to have warging and greensight powers, or at east the power to counter bran while he is using them.
The night king has been observing the south this whole time, observing Jon and Dany, waiting until they are in love, to march on eastwatch, its been what a year or more since hardholme, if he could cross the wall he would have done it.
Sam: He had Sam spared way back at the fist of the firstmen because he knew he and Jon were friends and that Sam a bookish boy would eventually become a Maester, that would eventually lead jon to the the massive dragonglass deposit on dragonstone, and into Dany's heart.
Bran: I always wondered how Meera managed to escape such a massive horde of tireless undead while hauling bran, the night king let her go, sent a few wights to make a show of it sure, but let her go so Bran would be around to send the ravens to spy on him and alert Jon on dragonstone to make him come north of the wall again.
Jon: He wanted Jon to lead a party or army north past the wall, so he could captured him and lure Dany and her dragons out past it. So he could kill one to melt the wall
Archmaester Ebrose was right and the wall would have protected everyone till Jon Sam and Bran fucked things up, if they had just done nothing he would have just stayed trapped beyond the wall stuck in impotent rage.