The Spaniard revealed in a rant on Wednesday that he would not be in charge of the Blues beyond the end of the season, and criticised his tag as the interim manager.
However, Cundy believes that the former Liverpool boss should never have been given the job in the first place.
"I cannot accept that Benitez was surprised to be called interim manager because at the end of the day, Avram Grant and Robby Di Matteo had that title and they both got Chelsea to a Champions League final," Cundy said on talkSPORT.
"Benitez has not helped himself because if Chelsea were winning and had been playing attractive football over the last few months, it would have quietened the fans. The trouble is they have not been playing well.
"He should never have been offered the job and while I have a little sympathy with him for what has gone on, you cannot come out and attack the owner and have a go at the fans. You cannot get away with that, you can't."
Benitez took over at Stamford Bridge after Roberto Di Matteo was sacked in November.