Why is Cyborg in Doom Patrol instead of Titans?

Screenrant explains the change and connections, suggesting that Cyborg fits thematically in couple of ways, is connected to Doom Patrol in a secondary way, and believes his presence will help attract viewers.

...While Victor Stone was never a part of the Doom Patrol in any comic book series, he would be a perfect fit for the team thematically. Every member of the classic Doom Patrol had their life endangered by a horrible accident and was saved only by an experimental treatment conceived by Dr. Niles Caulder. It could be argued, however, that death would have been preferable to Dr. Caulder's cures, which left his patients as something both more and less than human and often wishing that they had been allowed to die. This was the exact same state that young Victor Stone was in immediately following his father's efforts to save his life.

Though Cyborg was created nearly two decades after the first Doom Patrol comics were published, his origin story fit the same tragic mold as Elasti-Woman and Negative Man. The body horror parallels are particularly strong between Cyborg and Robotman, whose brain was transplanted into a super-strong and almost unbreakable robot body that was also incapable of smelling, tasting or any fine sense of touch. Given that, it is surprising that a connection between Cyborg and the Doom Patrol has never been established before now. This seems particularly strange given that Cyborg's closest friend in the comics, Beast Boy, was a member of the Doom Patrol before he joined the New Teen Titans.

Beyond the thematic connections, Cyborg's induction into the Doom Patrol will also serve to attract casual comics fans to the new series and offer them an accessible frame of reference.

And to help confirm Screenrant's assessment, actor Joivain Wade (Cyborg) basically says nearly the same thing, but with the notion that *maybe this is how Cyborg becomes the character he is in Teen Titans, *should that be DC TV series' plan...

"Every single person in the Doom Patrol has gone through traumatic, unfortunate events which have given them some kind of dysfunction or disability," Wade says. "Vic has turned his into something good, whereas the rest of the guys are essentially learning how to turn theirs into something good. But when it comes to him learning and growing and becoming who he's meant to be, who better to learn from than a bunch of characters who have also gone through similar things? It's been a greater playground for him to be discovering and learning about himself to then be ready to join the Titans when the DCU decides to do that."