I've always thought that the choice between Mother Abigail's selfish old testament god and a creature of destruction doomed to fail in his attempt to create was a stupid fucking choice. If I am to take these two sides and their representatives seriously than fuck all that noise you can catch me on the east coast. The building military confrontation teased though the entire second half of the book that never happens to instead have the literal Hand of God destroy Las Vegas including the entire population? Terrible ending. These are people that we've learned aren't all villains. Some just threw in with what they saw as order. Given that the world nearly ended who can blame someone for siding with the first person that looked able to get the power back on? God I guess. Atomic hellfire for all of you as another King villain is hoisted by their own petard rather than being bested by the heroes.
But I still really like the book even though I think the themes are fucked and the ending is trash. Why? Because of the characters. The book's long as fuck so you just get all this time to hang out with Stu, Harold, Lloyd, Trash, Flagg, Nick, etc. Also, the Captain Trips stuff in the beginning is all A+. A 1970s coked out-of-his-mind King really paints a wonderful nightmare of an omni-powerful government and its jackbooted thugs stamping out descent as the plague spreads. The first couple hundred pages are such a good time.
The show gave us no time to hang out with anyone but Harold and it's already almost over. Episode 7 should be the walk to Vegas, episode 8 the confrontation and episode 9 the wrapping up. That's it. We're done. Telling the story out of order for the first couple of episodes made no fucking sense. All the music selections are cheap shortcuts of storytelling or character development. Oh shit, remember Don't Fear the Reaper? Here's a tiny bit of it at the end of an episode. Hey, it's Heather Graham! Let's use Brand New Key! Remember Boogie Nights? Why yes I do remember Boogie Nights and I would very much rather be watching that now instead.
In regards to Flagg specifically his power wanes because he's a King villain. Through no involvement by the heroes his magical sight dims. Dayna kills herself before telling him who the moon man is, the Judge gets shot in the face so he can't send the head back like he wanted, Tom escapes, Nadine baits him in to killing her and by extension their unborn child, people are starting to escape the Las Vegas, Trashcan Man flies off the handle when someone makes "people who play with fire wet the bed" joke in passing while he's working at a military base. Trash then booby traps fucking everything killing every single pilot Flagg has plus all the pilots in training plus a bunch of other people and equipment. Then Trash goes in to the desert to find the biggest fire he can and when he brings it back to Vegas a bit of power that Flagg lets loose grows beyond his control before taking the shape of god's hand and setting off the nuke as a couple remaining "good guys" get reduced to atomic residue.
The "heroes" do nothing but show up to witness from ground zero Mother Abigail's god cook Vegas at 5000 degrees.