The episode continues from episode 5 where Captain Carter gets pulled into the 1602 universe. It’s a bit confusing and they don’t make things specifically clear, but the end saves the entire episode otherwise it would have been a huge mish-mash of complete trash.
It’s still confusing but basically – this is my take at least – not one but many universes are colliding; hence why The Avengers characters all from different universes are in 1602. There is not just one Forerunner, they are all Foreunners and that is why they all disappear at the end when the Time Stone is used. There are a bunch of plot holes, but in order to get everything to work, it’s more Marvel’s let’s fit the square peg in the round hole type of storytelling.
So The Avengers being from different universes explains why Happy Hogan can turn into the Purple Hulk and why Banner is the Hulk. Otherwise, in the year 1602, Banner would have had to somehow come up with the equivalent of a gamma bomb, and Happy somehow was injected with Hulk blood. You could argue magic, etc. but you’ll notice the episode never explains anything. The same with Thor, Loki, and Hela who apparently are Asgardians as Thor is called the Odinson. In this universe, for whatever reason and conveniently, the Time Stone is used in the Sceptre, but the Asgardians don’t know what Infinity Stones are, I guess. Or for another unexplained reason, and it further proves they are all from different universes, similar to Steve Rogers, they all forgot.
Update: Another interpretation is that all The Avengers characters are from the same universe. So when Steve hits the Time Stone, it sends them all to the 1602 and causes the two universes to collapse on one another. From that, we are then to assume in Steve’s original universe, Loki and Hela aren’t dead, I guess, as they are merged into the 1602. Again, confusing and they really don’t hint or explain what is going on.
Lots of head-scratching
Now regarding Steve Rogers, in his universe, he hits the Time Stone with his shield which transports him to the 1602 universe and he forgets everything (again, why?). Well, something new is the Time Stone has Multiversal powers, I guess. There is also the fact that the Infinity Stones only work in their respective universe so how can they transport people through the Multiverse? Well, it’s probably different for the MCU, is the argument, of course. More Marvel “let’s fit the square peg in the round hole” storytelling.
Oh, how about since this is a take on the Robin Hood story, where Robin Hood is known for using bow and arrows, where’s Marvel’s bow and arrow guy? No, Hawekeye lol. The reason there is no Hawkeye is that the episode is all about pushing Captain Carter. Obviously, it wouldn’t have made sense for Scarlet Witch to rip Captain Carter out of her universe to track down Hawkeye as the Forerunner, right?
Here is another one: So Tony’s device reveals who the Forerunner is and sends the Forerunner back to their own universe. Again, when the Time Stone is used, it sends everyone back to their universe. Everyone except for Captain Carter who is also from a different universe. That didn’t make sense at all unless it’s because Scarlet Witch brought her there, but again, nothing is explained.
Final thought: It’s another What If episode that needed to be better fleshed out. It again had the potential to be really good but seemed rushed and it’s more important to push a diverse Captain America character replacement onto the fandom than to come up with a good story. They built the story around Captain Carter and got everything to fit: let’s fit the square peg in the round hole.
