@lingeringperception restricted comments on this thread, so I have to add to it this way: There’s a VERY simple explanation for the “Did Cap let atrocities happen?” question. The answer is: The TVA. As established, any attempts to change the sacred timeline would result in timeline branching and therefore pruning by TVA. He might’ve attempted to and been pruned each time. If Steve did remain in the past, then Steve that got old would have HAD to allow the established events to unfold.