I saw that there is a recent trend in splitting the sign-in step into two: login followed by password (rather than in a single stage). That is, the flow is:
[type username] -> [confirm] -> [type password] -> [confirm].
For example, here is how does it work at Amazon and DocuSign:
Personally, I find this UI annoying, as it adds one more unnecessary step. Even worse, it makes it harder to use password managers (such as 1Password).
So, what are the reasons for the username/password step split?