Campbell terminated his five-year deal with League Two Notts County and looks as though he will be unable to play for another club until January.
But Wenger said: "He knew straight away that's not where is challenge is.
"It is always a cultural shock when you go down a level. I know from talking to players who have had to do that. They experienced it badly in the first six months and you can understand why they decided to quit.
"I believe Sol still has enough in the locker to play in the Premier League."
Wenger said he had not been surprised by Campbell's sudden change of heart.
"I knew it would be difficult for him there," he said.