can't launch gedit after using sudo -i

I have been 'cleaning up' a base system I use for cloning in VirtualBox. Don't recall removing anything 'important' :dis: but must have because now when I issue 'sudo -i' then the password, it gets to root ok, but now if I run an app like gedit, it complains with the messages
Setting aside all the parms that could be supplied, what might be the cause of this change?

TIA