Just off the top of my head...
Mustafi - £35m
Xhaka - £30m
Lacazette - £45m
Lucas Perez - £17m
Mkhitaryan bought in on huge wages.
It's not that he wasn't backed, it's that the money wasn't spent on the right players. And I haven't mentioned the famous summer of 2015 when, apparently, he was completely unable to find a single outfield player to improve a squad that had finished third.
Look, Wenger - at his peak - was a genius. I've watched, and loved the film about him, but I think we all need to remember that a large part of the mess Mikel Arteta has spent two years cleaning up was created by Le Boss.