Tim got established as a vigilante because unlike in canon, when Bruce started going off the rails, he knew enough to bench himself, and (reluctantly) handed Gotham off temporally to the various bat-approved superhero groups in Gotham. But that still left most of them stretched thin, and Tim saw a need for someone in the area around his home. It’s rich, upper-class Gotham, yes, but there are still poor people operating in and arround the area, who are vulnerable to crime and abuse. Nobody’s policing his neighborhood, though, because it’s officially a ‘safe’ part of town. So Tim takes up a mantle, and expands out from there.
Despite Tim being a non-aligned vigilante without many ties to the superhero community in whole, he’s an established enough force in his patch of Gotham to be noted. So when identity crisis roles around, his dad is still killed (Because the one who arranged it assumed Tim must have had stronger ties to the community than he did.) only Batman isn’t there.
Enter Owen Mercer, Captain Boomerang the second. Literally. Here, there’s no Batman, only a severely shaken Tim-in-civvies and a bunch of Gotham’s less-than-finest. Owen, who isn’t a complete asshole, ends up bonding/grieving/circumventing the cops with Tim to get to their dads, and ends up sucked into Tim’s little group.
Owen is the PoV character, and we see through his eyes how Tim operates in Gotham, how Ives, Ariana, and Dana act as his support network and family, and how Jason/Red Hood plays into things.