I just finished two tutorials related to SPA Angular authentication and NestJS API set-up and integration.
After I finished most of the Angular application configuration tutorial, the universal login page used to look like this one:
I configured it at the beginning and it appears on the Branding>Universal Login page of my tenant.
However, after I finished the tutorial for API configuration and integrated it with my client side. The universal login page changed its appearance to this:

How can I revert the appearance of the universal login page to what it looked like before API integration? And what's the cause of this behavior?