To me, Google's two step sign in seemed like a step backward in usability when they first introduced this extra step of clicking 'next' to enter the password. However, I realized that this solves a very important problem for G Suite users.
While using Google's apps that are configured for companies/organizations, the employees or organization members had to remember the URL to log into the app (like gmail.myorganization.com). Essentially these were Google's products, but one could not use them by simply going to Google.com. Google seems to have identified as a problem they could solve, and they now route users to the organization's sign in pages when you type in an email which is configured with G Suite.
To illustrate this further, I observed that a lot of the students in my University were simply going to google.com to log into their University email. Google understands that they meant to sign into their organizational account, and takes them to the University's SSO page.
If the users of your app usually visit your website to log into their own portal, you should be following this approach too.