Almost the entire episode is literally just an exposition dump on the multiverse to set up an excuse to bring it back.
i watched dan murrell's review of the episode and he said it was like the architect scene in the matrix reloaded. that's EXACTLY how i felt.
it's not completely the same because he who remains (ok, i won't be presumptuous and call him kang - according to wikipedia he's more like immortus than kang anyway? whatever) is a way more entertaining character than the architect. but it is a similar "a new character appears completely out of the blue and explains things to the protagonist (really the audience) for a ton of time" kind of thing. lazy writing.