reportedly, the moving of Kang into full antagonist was a covid thing - that he was actually going to only show up in a mid-credit reveal like most speculated (that same reporting didn't come with a reason why)
also no specific information about what would have been in Kang's place, but biggest guess was Miss Minutes having a much bigger interaction - the previews showed Loki sitting on the throne in Asgard, which we never saw in the show, so maybe MM showed Loki and Sylvie what their temptation actually looked like