By using terms such as "culprit", "idiot", and "turkey" you indicate that you are a big part of the problem.
Only gross mismanagement would let you get into such a mess in the first place.
It sounds like he is well rid of you.
Parent post should be modded up +5 insightful.
I agree this poster does sound like a very poor manager or the company he works for has management issues.
What training programs do you have in place ?
Was this person doing a poor job because of company work practices ?
Was he faking that he knew what he was doing because no one showed him how to do it properly ?
If these above questions could be answered then I think you would find that you would not need to be asking
what to do after your Sysadmin / developer went off and found greener pastures.