I tried to set up Outlook 365 but I entered the wrong credentials. For some reason, which there is no point investigating further at this stage, I managed to crash Outlook 365. I was stuck with the forever loading splash screen of Outlook. There was no way for me to change the values from that loading interface. On top of that I believe the profile data file was corrupted, so there was no way to start Outlook at this stage.
So, I had to reset Outlook 365 like it was the first time it was being used:
So, I had to reset Outlook 365 like it was the first time it was being used: