Saturday will mark the first anniversary of the terror attack on the team bus in the Angolan enclave of Cabinda ahead of last year's Africa Cup of Nations.
Wenger signed Adebayor from Monaco at the age of 21 for only £3million and sold him to City three and a half years later for £25m.
Wenger said: "I think what happened with the national team had an influence on his mind because last year before he went to the African Nations Cup he was doing extremely well. What happened was not a small incident and for the rest of the season certainly it had an impact.
"Adebayor also maybe a victim of too much competition. He is a player who needs confidence. He needs to feel that he is a regular. It depends, every case is different."
Wenger also slammed claims Adebayor was a "high maintenance" player.
Wenger said: "The only idea I fight against is that he is high maintenance. He is not high maintenance. We he comes in, in the morning, he is on time. He works well. He is never disrespectful. He is a top class player and attitude-wise, we had no problem with him."