I have around 8-9 friends who are either vets/doctors (plus one engineer) and are Arsenal fans. literally every single one of them is a fan of Wenger (and hate the owners). It seems that the Arsenal fans who are anti-wenger on social media are all the thick, uneducated ones (sorry for rude/controversial statement).
They say that not only was he a great coach and statesman for the club but he did a few things which no other coach did:
1) He shielded the owners and board from criticism, and unlike pretty much every other manager never blamed them for bad results or seasons e.g. when coaches talk about lack of funds. This is the reason why everyone from Dein, kroenke etc... loves Wenger. He made their life so much easier than if anyone else was coach.
2) He actually saved the club a huge amount of money and was always looking into how to reduce costs, he had a big interest in administration of the club and financial meetings which other coaches don't care about. This was critical during the transition period of paying for a huge new stadium amid a time that oligarchs were pouring money into Arsenal's rivals.
These guys are saying that arsenal will be the equivalent of everton now that wenger leaves (I would say they were also the equivalent of everton before he joined).