In What If...?, in the finale, Uatu the Watcher is the only one concerned about the multi-universe when

Ultron with the Infinity Stones plans to conquer the multiverse.

Why is Uatu the only one concerned about or who wants to save the multiverse? Why don't other cosmic beings interfere at this point?

Related questions that come to my mind and that can lead to an answer:

Could it be that other cosmic beings thought Uatu will handle it? or Could it be that they don't know yet how big a threat Ultron is? Couldn't Uatu ask other cosmic beings for help? Could it be that he knew the Evil Doctor Strange is more powerful than many cosmic beings and wanted to devise a plan with him?

From the plot standpoint, it would get complicated to include many cosmic beings. However, there can be an in-universe answer also.

Edit: Adding some key information I've missed.

"I have seen everything that has ever happened. Ever will happen. Ever could happen." ―The Watcher

"Uatu and Strange went back to Strange's dimension, the Mirror Dimension, where Strange pointed out how Uatu knew how the battle would unfold before it started as well as Killmonger's betrayal. Uatu then thanked Strange for helping him and his sacrifice to keep watch over the pocket dimension." https://marvelcinematicuniverse.fandom.com/wiki/The_Watcher

It looks like The Watcher has seen all outcomes in all timelines. However, when Ultron breaks into Nexus of All Realities to fight with him, he says: "I don't understand. This should not be possible."

It looks like this is the only thing he didn't see but then based on what Strange said it is implied that he knew how the battle will unfold.

It is not part of MCU currently but there are supposed to be the Protectors of the Multiverse.

"The Multiverse was originally categorized and protected by Merlyn, who established the Captain Britain Corps."

"There are other beings and groups dealing with protecting the Multiverse, for example the Time Variance Authority, or the Exiles." https://marvel.fandom.com/wiki/Multiverse

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    It looks like a question that could be answered in season 2.
    – Taladris
    Nov 18, 2021 at 3:52
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    @0.. - Could you specify the cosmic beings you have in mind here? The answer/s might vary depending on the beings in question. Nov 18, 2021 at 4:05
  • @LogicDictates Any cosmic being like abstract entities, celestials etc. or even Living Tribunal. Why wouldn't any other cosmic being be concerned and interfere when the whole Multiverse is threatened?
    – ermanen
    Nov 18, 2021 at 4:26
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    @0.. - The problem with answering this question is that we know next to nothing about the MCU versions of the beings you're talking about. For example, did Ultron kill all the versions of these being native to his own universe in What If...? episode 8? It was implied that he was alone in his universe at one point, but we don't know whether that means he killed literally every other being in his universe, including the abstracts, or just the non-abstracts. Nov 18, 2021 at 5:08
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    So far, the Watcher is the only being we’ve seen in the MCU who can observe different universes — unless He Who Remains in Loki is doing the same thing, which is currently unclear. Nov 18, 2021 at 12:09