Wrong user name/profile in registry

Recently changed name of a user account. Thought it was straight forward but I started getting the dreaded "We can not sign into your account" error. Off to the registry, under this user's account, where I noticed the old username with the Temp designation but it wouldn't let me delete the temporary user profile. Tried going in under my account (admin) and the temp user profile was gone but so too was the new user account. However, one of the registry user profile entries had the ".bak" extension.

I know I'm doing something wrong but don't know what it is (I learned this from being married for over 35 years and using computers for about as long ). Help?

Yes, I did change through MS account but the key is in the intro to the tutorial where it states changing an account name doesn't change the profile name. I went into the registry and simply changed the old username to the new one and it seems to be working fine, for now. I hope that is enough.

Not sure why MS wouldn't change the profile name along with a username change. Scratching my head trying to think of scenarios where most users would need a different username and profile name. Oh, well. Way beyond me.