You might be right. Amazing Spider-Man 2 took a lot of money, but not the amount that Sony was expecting. Hence why he's partially gone back to Marvel, Sony realised dey dun fuct up. Yes, Batman is a massive cultural behemoth, so granted numbers will be large, but I don't think people are that stupid to go and watch a film just because of a character. Back in '97 people steered clear of a Batman film that was teeming with some of the biggest names in cinema (at the time). That was because of the negative critique it received which people have way more access to than they did back then.
Fully agreed on the Joker imagery though. It's too contrived.