I feel everyone’s given their thoughts on the Dabi/Toya theory so I’ll keep it brief. Do I think Dabi is secretly Toya? Yes.
Now, here’s the real question: Why hasn’t anyone, especially the Todoroki Family, figured it out yet? Well, here’s what I think.
There’re several answers as to why Dabi’s true identity’s still hidden. His disfigured body, Enji (or Rei) never getting a good look at him up close, but I think the most important reason is Toya’s dead. Okay, maybe I should say presumed dead. We’ve seen the police and government in the series be pretty competent. Learning the location of the League of Villain’s bar as well as most of their true identities, adjusting the provisional license exam to deal with a post-All Might world, and sending Hawks undercover after the League. These people know their stuff, so there has to be a very good reason why no one’s assumed a missing Toya is Dabi. That reason has to be there is no missing Toya, he’s supposed to be dead. What happened? No clue. But, I’m guessing a reason why Dabi was drawn to Stain’s ideals is because of his forgotten hatred of Endeavor.
Forgotten, you say? Yep, you heard right. The reason Dabi never talks about the Todoroki family on a personal level, the reason he hasn’t outed himself as Endeavor’s son, wreaking the number one heroes’ reputation is that he doesn’t remember his past. Dabi forgetting all about Snatch might be a clue he lost his memories in whatever accident that presumably killed Toya. It’s not personal with the Todorokis because he doesn’t remember being one. But, his hatred of heroes (at least Endeavor) is still in there somewhere, which lead him down a dark path.
So, assuming this is all true, how’s Dabi gonna get his memories back? Simple. Someone will finally recognize him. Not Shoto, he barely knew Toya, so it’d have to be Enji Todoroki. Like with Snatch, if Enji drops Toya’s name, Dabi’s memories may start returning. And then, dear fans, we’ll get that sweet sweet Dabi flashback.
There you have it. Why I think no one considers Dabi to be Toya in the series. When will it be revealed? Who knows. There’s still the issue with the U.A. traitor and Kaminari being connected to the Meta Liberation Army to sort out along with whether Best Jeanist is truly dead. Mysteries are piling up and since Shigaraki got his backstory fairly recently, I don’t see Dabi getting his anytime soon. So, sit back and relax and look for more clues hinting at Dabi’s true identity. For all we know, he could be someone else entirely. Hey! Maybe he’s actually Deku’s dad from an alternate dimension where non-powered humans destroyed most quirk users. Hm. I better write that down just in case.