This is indicative of something having gone wrong with your Plasma configuration. Unfortunately, this does happen from time to time. Two weeks ago I lost all usability of my Plasma desktop, as you can read on this thread, along with how I’ve eventually solved it with the help of the community.
However, if you got the default Manjaro wallpaper back, then you were lucky, because then that means that Plasma was able to reset itself to the default settings. Not everyone is that lucky.
That said, considering that you’re also having problems with your zsh history and that the file was corrupted while it’s only a plain text file, there may be something else going on here. Either you had an unclean shutdown — e.g. by pressing the reset button on the computer housing, or by a power outage — or you may have a hardware problem going on, and in that case, the SSD drive would be a likely culprit.
Right-click the desktop, choose “Configure Desktop and Wallpaper”, and check whether your desktop is set to “Desktop” or “Folder View”. In the “Desktop” view, there are no icons on the desktop.
In “Folder View”, it’ll show whatever is in the designated folder as icons on your desktop — by default, this will be ~/Desktop, but you can pick any other folder if you wish.
Just nuke ~/.zhistory — it’s only a plain text file — and start building up a new history file.