The timescale of history in the MCU has me very confused, for a couple of reasons - but primarily, concerning the history of Asgard and its conflicts.
(Note: I do throw in a few other questions in the middle of this post, but I make sure to annotate them with "this is a different question" or something of the sort so I don't distract / detract from my main question - I just wanted to show my train of thought.)
So, we know from Thor: The Dark World that the Dark Elves existed before the current universe in the MCU - they existed in the total darkness before it. When the universe, and, along with it, the Nine Realms and all of the other parts of the cosmos, came into existence, the Dark Elves sought to return the universe to its previous state using the Reality Stone, a.k.a. the Aether.
Moreover, we also know that the plan Malekith carried out to engage in such "universal correction" occurred during the previous Convergence, when King Bor was ruler of Asgard, roughly 5000 years prior to the present day.
So, if I'm getting my math right, if the universe is indeed as we believe, roughly 14 billion years old, Malekith and his buddies just waited around nearly all of existence to attack Asgard 5000 years ago / 3000 BC? (And for that matter, how long has Asgard been around? Given that the first king of Asgard was Buri, Bor's father, and Asgardians live a couple thousand years, I'm not sure how far back it can go. Though, this is another question entirely.)
So, if the Convergence really did take place every 5000 years, and the universe is presumably much older than that, Malekith would have had various - and I mean various - opportunities to carry out his plan on any of the Nine Realms. And for that matter, given the sheer timescale of existence that we might assume for the universe, and the fact that the Dark Elves have spacefaring ships, they could definitely attack civilizations not linked by the Convergence and carry out their plan that way.
(Quick note: Odin does say that
after eternities of bloodshed, my father Bor finally triumphed, ushering in a peace that lasted thousands of years.
This could be a possible answer to this question - but what does "eternities" mean here? Does Odin mean, like, universe-age eternities? That, for the near-entirety of existence, the Dark Elves were just ravaging the universe? Again, what's the time-scale here? How old is the universe?)
This really only makes sense if the age of the universe in the MCU was comparable to the time elapsing between each Convergence, because the Dark Elves would have ended up on Svartalfheim, which conveniently links to Asgard and other realms they can wreak havoc upon during the Convergence(s). So, either Malekith times his attacks on civilizations for perfect cinematic backstory, or the MCU universe is younger than we expect. (Or I'm missing some other crucial information.)