Grim + Aurora plot hole (?)

I reread Lightlark and Nightbane while reading Grim and Oro, I’d read the chapters from Isla‘s POV then from Grim‘s/ Oro’s immediately after and enjoyed experiencing the book this way so I highly recommend it!

the other reason I did this is because I didn’t love Skyshade and crowntide nearly as much as the first 2 books, so I wanted to bring back that feeling again because Crowntide made me really mad.

Anyway, now that I’ve been submerged into this world I‘m very confused about Grim’s motivation for working with Aurora. When book 1 ends, we learn that his reason for doing this was to break the curses, because Aurora tricked him that the original offense was a Sunling ruler falling in love with a Wildling ruler. Fair enough. he worked with her to break the curses and live happily ever after with Isla afterward.

Nightbane spoilers below!

however in Nightbane, we learn that Isla has been dead this whole time, so she can’t really live happily ever after with Grim even after the curses are broken, which they now are. and in Nightbane Grim claims that he waged a war to bring her back from the dead. OK fair I guess, but that makes the entire plot of his book 1 alliance with Aurora make no sense - breaking the curses wouldn’t have helped in bringing Isla back from the dead. And Grim has never cared about breaking the curses anyway. so why was he aligning with Aurora then and basically wasting time with that plan instead of figuring out a way how to revive Isla? I’m very confused.

Grim’s betrayal in book 1 is very related to his working with Aurora, so if I’m ever going to get on board with Grim being end game I need to know why he’d align with the greatest evil their world has ever seen, and I’m falling short. I need an explanation if I’m ever going to forgive him, all of skyshade and Crowntide didn‘t convince me to get on team Grim.

a possible solution I see is that had Aurora‘s plan been genuine, Grim would have killed Oro as planned and after the curses were broken use the portal on Lightlark to save Isla. And if that was indeed his reasoning, perhaps Alex didnt reveal it to us in Lightlark so she doesn’t spoil the fact that Isla is dead, but that would also mean that when Grim explains to her why he took her memories he is yet again not truthful and forthcoming with her. but we’ve had 4 books since then for him to explain what his plan with Aurora was and whether my speculation of him planing to use the portal after Oro was dead in an alt ending of Lightlark book 1 is accurate.. and it hasn’t happened. Whatever the explanation is, we need it!

am I missing something? Please enlighten me if I am. This is nagging me a lot as I’m trying to prepare for the last book in which Grim and isla are endgame