Dylan O'Brien would be a horrible Dick Grayson. He would be terrible in any role. He's not a good actor. I personally think Timothee Chalamet would be the best Dick Grayson/Nightwing, at least as far as older characters go. The problem with casting for the Robins is age. It largely depends on two factors; what the vision of the director is, and at what point in Batman's career does the movie/show take place. If you wanna start with the first Robin, early in Batman's career, then you have to cast a teen. Someone around 10-14, as that is the traditional age range of Dick Grayson in the comics. And casting children is difficult because of puberty and the length of production. That doesn't mean it can't be done, just that it makes things much more difficult. That's why so many people prefer to tell stories where Batman is older. Then you have a grown up Dick Grayson, much easier to cast. Personally, I don't care too much for Dick. If I had to rate all the Robins, he would be in the lower end for me. I prefer Jason Todd. And I hope to see more people give him (or any of the other Robins) the appreciation they deserve. The great thing about Jason Todd is that you can cast for someone in their later teens. Makes it much easier. He starts as Robin at around 13, but the bulk of his interesting exploits as Robin happen closer to his death at 17. So, if you wanted to do a Batman story where Batman is older, and Dick Grayson is an adult, then you could have Jason as the Robin. You could cast for someone between 15-19 and they'll likely be able to convincingly play a 16/17 year-old no problem. Maybe even younger if they're a late-bloomer or naturally youthful in appearance. But I'm going on a tangent, my apologies. Dylan O'Brian is a bad casting choice, I completely agree with you. As of 2022, if I had to cast the Robins, I would do so in a world where Bruce is in his 40's. I would cast Timothee Chalamet as Dick Grayson. I would cast Maxwell Jenkins as Jason Todd. And I would cast Javon Walton as Tim Drake.

Man, like this... I don't understand it either, to be honest, but I re-followed Dylan's acting career and from what I've seen he makes a lot of stunt movies with Maze Ranner and his appearance reminds me a lot of Dick Grayson from the animation "Batman's son " where Dick Grayson appears and you see him without the costume reminds him a little of Dylan O'brian and he is also compared a lot with Nightwing from the Titans series.