I subscribe to the theory that the Conqueror is actually a younger He Who Remains at an earlier point in his timeline, before he succeeded in achieving total control by culling all of his other variants.

And the multiverse stuff is absolutely related to the Sacred Timeline being unshackled. The TVA would have pruned all those other timelines before they caused incursions. But they stopped pruning, and we get What If…?, No Way Home, and Multiverse of Madness, plus everything else to come.