The introduction of the Illuminati was one of the biggest developments in Spider-Man: No Way Home. Directed by Sam Raimi, Multiverse of Madness departed from the standard MCU formula in many ways, while also delving much more into the horror realm than ever before.
On the surface, the appearance of the Illuminati in Doctor Strange in the Multiverse of Madness should have been a moment of triumph for Marvel devotees, especially due to John Krasinski's long-demanded casting as Reed Richards. Any triumphant feeling was short-lived thanks to Doctor Strange 2's decision to subvert expectations by almost immediately killing this new group of powerful heroes off. Not only did they die, but they got utterly trounced and destroyed by a Darkhold-powered Scarlet Witch.
While many were put off by just how easily the Illuminati were offed, it is important to that none of them were from the main MCU world, Earth-616. That means multiverse variants of Reed Richards, Professor X, Captain Carter, and the rest of the Illuminati are likely to reappear in future movies. Then again, it may actually be in the cards that the Earth-838 Illuminati will themselves be resurrected. After all, Doctor Strange 2 ends with Clea showing up to enlist Strange with help fixing an incursion he himself caused. The murder of the 838 Illuminati may well be related to the incursion in question.
Of course, since the Earth-838 Illuminati are already dead, that means Doctor Strange and Clea will have to make use of not only multiversal travel but time travel. The MCU has done plenty of both as of late, so it is not hard to imagine Strange and Clea getting up to some quantum shenanigans that might draw the attention of the TVA in order to undo such a catastrophic loss of Earth-838's most brilliant minds, minds which may well be needed to solve further multiversal messes later on. Kang the Conqueror is arriving soon after all.
Strange and Clea altering the Earth-838 timeline may also finally prove once and for all how time travel works in the MCU, as despite Hulk's explanation of Avengers: Endgame, events have happened since that don't jive with the idea that the past can't be changed in a way that effects the future of that same timeline. Either way, any Doctor Strange in the Multiverse of Madness watchers upset about the demise of Illuminati Reed Richards, Professor X, Captain Carter, Black Bolt, and Maria Rambeau's Captain Marvel likely will not have to wait long to see them appear again onscreen. As the Marvel universe has illustrated so many times, death is often only a temporary condition.
