https://www.superherohype.com/tv/427971-arrowverse-producers-explain-batmans-absence-from-elseworlds
According to Dries, the Arrowverse version of Batman has been MIA for years, allowing Gotham City's crime rate to rise. "Our approach is: What does Gotham look like after the Batman has been gone for three years?" Dries told EW. "So if you have the law and order, protector, and hope gone, what happens as a result? Some people are thriving in his absence because now they can start to do their own thing without the oversight. A lot of other people are suffering and they're losing hope, and the city itself and infrastructure is falling apart. So it's not a happy place. Our guys walk into a grimy, scary Gotham."