What went wrong is when the campaign against him,about 4th not being a trophy, really ramped up after 15/16 season, coming 2nd, Wenger doubted himself and started to change his style. It was quite noticeable at times watching the team sit back against City, hoping to catch them in the break. That wasn’t Wenger. He gave in to the social media trolls. And when the memes, protests and planes hit the games it was all over. We had two years of decline and nervousness.
Wenger should have gone earlier.
So he gave into the campaign about not being good enough to change his style, even though that style made us one of the top teams for a fair old while? Is that why he started buying lesser players as well? And why we lacked real balls on the pitch?
IMO what happened was that he managed us brilliantly into the Emirates, however he overpaid a lot of average players...and then after years of selling our best players and hardly spending we had the ability to spend - the problem was it didn't happen at the right rate or quality.
Outside of Özil and Sanchez the quality was lacking, especially in defensive areas which was always a Wenger weakness. I'm not really blaming Wenger (as such) but a lot changed during his time at Arsenal - we had the restraints of the stadium move and then things were compounded by the rich owners coming in...I truly believe if that never happened we'd be top dogs today with Wenger still at the helm.
Football changed but we couldn't adapt and was left behind...now we are left trying to compete for the top 4 that was previously touted as not good enough.