I'm back, too.
Because Tim Burton didn't wanna just do the same thing in the second one. He didn't wanna be repetitive so in Batman Returns Michael Keaton's Batman is put in different situations where he can't just rely on the same methods. In Batman '89 his foes are in areas that he can hide and can sneak-up from behind [two hoods on a lonely rooftop, Jack Nicholson's Jack Napier in a huge chemical factory, Joker taking Vicki hostage in a huge cathedral]. In Batman Returns his foes are out in the open on the streets terrorizing Gotham [the Red Triangle Circus Gang on Gotham Plaza, on Gotham Square, Michelle's Catwoman and Danny DeVito's Penguin outside Shreck's department store, Penguin at the Arctic World] where Keaton's Batman can't just go "it's a little bright, so I'll just sit this one out" and wait and hide in the shadows, no! He's gotta get out there and fight fire with fire out on the streets in the open, he doesn't really have a choice in those situations, but he's still not running around in the day and he's not openly hanging around Pat Hingle's burly gruff irascible Commissioner Gordon and the police chief in the Commissioner's office like Adam West's Batman would do with Neil Hamilton's Commissioner Gordon and Stafford Repp's Chief O'Hara in the Dozierverse, and like Val Kilmer's/George Clooney's Batman would do with the the Schumacherverse bumbling naive inept Pat Hingle Commissioner Gordon. The Burtonverse Michael Keaton Batman's still mysterious and wants to hide in the shadows, but in Batman Returns he's forced into unconformable situations. It's interesting to see Keaton's Batman forced out of his comfort zone.
In Fantasy Zone #1 (1989) Tim Burton explained, "I'm only interested in doing a sequel if you can do something more interesting than the first, and more it's own thing. I don't know if they [Warners] are prepared to make a sequel as interesting as it needs to be, and take it to the next level. I think it must get weirder before it gets anything else. I don't mean that in an abstract way, I mean that in a way that's interesting."
Batman- The 1989 Film: Vintage Magazine Article: "Fantasy Zone" #1 October 1989
Tim Burton explained in his foreword to Batman Returns: The Official Movie Book (1992) by Michael Singer, "One of the reasons I wanted to direct Batman Returns was to introduce different characters who are both very interesting and very complex, like The Penguin, Catwoman, Max Shreck and the Red Triangle Circus Gang. The Batman stories had some of the wildest characters in comics, yet for some reason, they seemed the most real to me. It's a challenge to make these characters come alive for movie audiences of the '90s... I feel like a real kindred spirit with Danny [DeVito], and I think we're creating something that people will see and enjoy as a natural expansion of the comic book character. I don't think there's anybody better at making the horrible acceptable."