Why was I signed out everywhere after changing my password?

That is intentional. Changing a password ends every other session on every other device and browser, keeping only the one you changed it from.

The main reason people change a password is that they suspect someone else has it. A new password would be pointless if the intruder's existing session simply carried on, so the change closes those sessions as well.

Sign in again with the new password wherever you use Creta.