I had this same problem about a month ago... what i did was navigate to the minecraft file, and moved out everything from that file to a folder on the desktop. The i downloaded and lanched a new minecraft. Finally i deleted everything from the new minecraft version exept the folder called “launcher” or something like that. Then i put everything from the folder on my desktop with the minecraft files back into the minecraft folder exept the old launcher folder
it could of been lightning or something that caught the house on fire...