I Interpreted it as Lancel was the gift and that Olenna or someone may have talked to the high sparrow about it. the high sparrow then got Lancel to talk, as he mentions how his soul was so heavy but now so light. I don't really buy that however since Lancel has been part of the religious cult since before it came into power. I think the high sparrow was just waiting to play the card. If he had tried to do it right away Cersei would have had them all killed.
No doubt in my mind Stannis sacrifices his daughter. They are just setting it up to be vile as possible for those of you who got all sappy when he talked about how much he loved his daughter.
There's no doubt in my mind that he doesn't, I believe it will cost him the war vs the Boltons, and there will be much wailing and gnashing of teeth among the fans. He'll probably get killed in some wintery battle having warned Shireen to find Ser Davos and get into hiding beforehand, just in case.
Once Stannis is gone Melly will turn her eye back towards Jon, who should be arriving back south of the wall with a massive army of wildlings. (Because seriously, Jon going up there only to get killed or rebuffed would be ridiculous storytelling.)
Sorry if this has already been answered but what gives with the faith militant/high sparrow having all this power to throw royalty in prison cells based on simple accusations? I mean to me they just seemed like some sort of underground cult/religion at first. Is it simply because the new boy king won't step in to stop it? It seems really stupid but maybe I'm just not understanding something here.
There have been tons of hints about this throughout each season. Remember the following:
-The old High Septon (their 'Pope') was a Lannister puppet who drank and whored and did as bid. Probably didn't even believe in god. But it's stated that the Crown and the Church are the two sources of all law and discipline. They need each other to keep the people under control. That's how it works. Just because we haven't seen much of the church doesn't mean it's not powerful. With the High Septon being a puppet, the Church and Crown have always been the same thing so far as the show has been running.
-The people were already rioting in the streets back in Joffrey's era. We saw preachers on the streets back then inciting violence too. So the people have been ready to follow someone.
-The war of five kings has reduced the numbers of guards severely, and has bankrupted the kingdom. People are starving.
-The 'High Sparrow' just redirects all of this pre-existing anger, using food to get people onside.
-The Sparrow makes a move against the High Septon, and incredibly Cersei decides to replace her puppet with the Sparrow. The Sparrow is now 'the official Pope'. So all the religious small folk must now follow him, not just his Sparrows.
-Then she decides to do something crazy, and arms the Sparrows, undoing a law saying that religious people couldn't be armed that had stood for hundreds of years. All of this is because she believes she controls the Sparrow (as she is the one who 'gave' him his power), and because he can bring down the hated Margaery.
-At this point, the Sparrow is both the leader of his cult and the official relgious leader of King's Landing (and possibly the whole kingdom) and has an entire city of starving, high religious people to do his bidding in a place where there's a weak king and a decimated army.
So he basically gains ludicrous power overnight, but it makes perfect sense in the world as presented.