I always saw The Powers that Be as the fates. There were three of them in Greek mythology and they were ported over to Roman mythology under different names. Clotho spun the thread that defined the fate of a human (Nona in Roman gods). Lachesis drew the lots to determine how long one lives and dispensed the thread (Roman Decuma) and Atropos carried out the death sentence by cutting the thread, causing death (Roman Morta). They had no concern over what people wanted or thought and there was no correlation in outcome. They are neither the good guys nor the bad guys.
I don't think they're as indifferent as that. We hear many times of Angel being a 'champion' for the Powers or a 'warrior' for their cause. W&H deliberately try to sever his connection to them - they wouldn't do that if the Powers were simply the fates. Whether for good or ill the PTBs are positioned as opposing forces to the Senior Partners.
Ultimately what
@WillowFromBuffy says is right. What is the alternative? Let the Black Thorn and the senior partners have their way? BUT also, bringing about the NFA battle still does nothing to stop the Senior Partners. Like The First evil, which will always be there, the Senior Partners will always be there. There will always be evil. Ultimately I think the answer is, there is no right answer, no easy choice.
I agree, there was no no easy choice to be made. Once he'd seen what was to come he had do to something at some point. Incidentally, I remember a while ago I was following some discussion threads about Angel's actions in Power Play/NFA (it might have even been on BB) where the question was raised of whether they all could have just walked away from W&H. I personally believe that it wouldn't have been that simple and I think the writers' did try to make this point earlier in the season:
GUNN: "Any thought about what would happen to us if we tried to say bye-bye? The ramifications, I mean. You think the senior partners are just gonna let us breeze on out the front door?" However, I don't think this was really impressed upon us beyond this scene - the difficulty of leaving the firm doesn't get mentioned again after this, and it's such a short exchange that most viewers probably forgot about it by the finale - so I can see it coming as a bit of a surprise for some viewers that Angel would choose all-out armageddon as his way out rather than just going back to helping the helpless from the Hyperion.
Yet the fact that taking out the BT didn't do anything to stop the Senior Partners raises the question of why they sent Angel that vision? Clearly they had an agenda against W&H, but how was it supposed to help in any other way? We don't even know the extent of their powers of foresight; if they are in some way benevolent powers, then would they not have known that LA would be sent to Hell, thus endangering thousands of lives?
@Grace has a great theory about how Cordelia's message delivery was just at the right time, when Angel was considering leaving W&H and who knows who she was working for!
With the way it turned out, isn't it kind of a "betrayal" either way? Either "real" unsuspecting Cordelia was telling Angel "you'll win this in the end" in service of getting him to pick a fight that would lead to him dying and/or bringing hell down on LA, or some evil was using her likeness to effectively do the same thing. Or I guess the third option is that "real" Cordelia dropped a very unclear vision on him and then wasn't able to set the record straight? But then, that's still another example of her ultimately being used.
I guess I just can't see any version of what happened with Cordelia in Season 5 as being good for her character when viewed in hindsight, though You're Welcome is very heartwarming on its own.
That is an interesting theory r.e. Cordy's timing. But I guess I was thinking of it being a betrayal of her character more from the writers' standpoint - would they really give us 'our' Cordy back for one episode, basically in reparation for what they did to her the previous season, only for it to be a ruse/dupe in some way? But then again we all know how evil Joss is...
What I also don't get is that 'You're Welcome' is supposed to be about Angel remembering what the original mission is - which is why we get to see Doyle's video again - yet that is kind of then swept aside by the vision. Angel even says in 'Power Play' that "This isn't a keep-fightin'- the-good-fight kind of deal." (although IMO the finale
did ultimately encapsulate the message of the show anyway)