This new direction specifically demands that EVERYTHING be under one roof.
If you're movie batman for example then you're also the voice of the animated version and all other media that follows.
They are allowing other productions to go ahead, with the Elseworlds label. Prime example being the Matt Reeves Batman films and spin-off TV shows, which Matt Reeves has relatively free reign for.
Now, with the DCU, they want the
actors to stay consistent across all media. Which, honestly, is a nice goal, but I can't see it being successful 100 percent. Even the MCU has had to replace some actors, and that was only in one medium.
Where was he? Why did he leave Gotham, which led to Roman Sionis aka Black Mask making an attempt to take over Gotham's crime scene? At first, I thought the Joker was dead. But he wasn't. Why did he leave Gotham after dumping Harley?
The Joker is not a crime boss. At least not in the traditional sense of organized crime. Well, maybe in Batman '89, and he took out the traditional organized crime bosses in TDK, but other than that, he's doing his own thing, which is mostly causing chaos and mayhem, not running illegal clubs and selling drugs. So, Sionis wouldn't have had to take over Gotham's crime scene from the Joker, because the Joker never was in charge of organized crime, not even in the DCEU. Yes, there is that one scene in the club where he is bargaining a criminal business deal, but there's no reason to believe he did that sort of thing all the time (more likely a way to fund his next crazy scheme), and there was certainly nothing saying he was in charge over all of Gotham's organized crime. In most interpretations, he leaves that sort of thing to characters like Penguin and, you know, Black Mask.
As to leaving Gotham, he does road trips all the time. He's often been in Metropolis (which is only across the river in the DCEU, which was always dumb). In the classic comic story A Death in the Family, he was in Ethiopia and later as UN Ambassador for Iran in Washington and New York. Hell, in the DCEU, he was in Central City, wasn't he?