Troubles with a user profile

On tuesday I helped a user becuase he wasn’t able to login to his computer the computer was stucked on the Windows welcome screen.

I asked the user if there was any updates done befor the default questions you know and because he told me that Windows did updates and it worked befor I though that the updates cause the problem so I’ve used the „last known good“ session but that does not help so I checked if I’m able to login with my account after half an houre of Windows is preparing your sassion screen I was finally loged in to the computer but it took a huge amount of time to get this far. I though maybe the computer is extremly slow and loged off again to try it again if it would work faster now, because it was my first login on this computer and that often takes some time, but the secound login was very fast actually and the user still wasn’t able to login, so I checked the user profile for corrupted files but I couldn’t find any and to make sure that it’s not the user profile I renamed the profile folder to [Username].old and asked the user to try it again it worked now so I copied the files from the old profile folder to the new folder and now it works. I’ve no idea why.