He knew Jason was killing people, and Batman couldn't live with the shame of knowing that he had unintentionally created a deadlier version of Joe Chill. This explains the tragedy of what kept Batman away but also highlights his own selfishness and irresponsibility.
Subsequent stories dealt with Batman's guilt over failing to save him. The character was resurrected in the 2005 "Under the Hood" story arc, which saw him becoming a murderous villain known as the Red Hood.
Batman considers this his greatest failure: not properly training Jason in his role as Robin, and failing to protect him from the Joker. In the years to come, he would erect a memorial in the Batcave made from Jason's uniform.
Blaming himself for Jason's death, a guilt-ridden Batman resolved to carry on alone. He even turned down Alfred's suggestion to involve Dick Grayson, his original partner.
Ironically, Bruce Wayne, the one person who truly loved Jason instead of manipulating him, was the one person whom Jason hated for the most of his life. Eventually, though, Jason and his surrogate father managed to return to talking terms, even forming a bond with one another similar to that which they used to have.
This is how lore accurate Batman would've beaten the Suicide Squad (Animation)
What did Batman do after Jason died?
Traumatized, Batman takes Jason and Sheila's remains to Gotham and holds a burial with Alfred Pennyworth, Commissioner James Gordon, and Barbara Gordon. Batman blames himself for Jason's death and resolves to carry on alone, rejecting Alfred's suggestion to involve Dick Grayson, the first Robin.
Ironically, he tried to steal a car to escape, which nodded to his carjacking days when Bruce found and converted him. But as he stared at the reflection, he saw himself and the Bat. He then lashed out, hating how Bruce let him go and never even bothered to look for him.
Jason's death and the events around it were so traumatic that Nightwing, when he was infected with fear toxin, one of the central themes of his nightmare was Jason's death as shown in Nightwing #10. Thankfully after Jason's revival, he and Nightwing have gotten the chance to foster an actual brotherly friendship.
Having said that, Jason was supposed to have been 15 when he died. (On his way to the Middle East to find his biological mother, he asks an airline attendant for a rum and coke.
The Joker murdered Jason, the second Robin, back in the 1988 Batman story arc "A Death in the Family." Jason did not stay dead, however, and was later resurrected thanks to some Multiverse-shattering events and a dip in one of Ra's al Ghul's Lazarus Pits, allowing for his transformation into the gun-toting vigilante, ...
Batman's three biggest personal failures are having his back broken by Bane, losing Jason Todd to the Joker, and giving Azrael the cowl. Bane breaking Batman's back was Bruce Wayne's most significant defeat, as the villain outsmarted and outplanned Batman at every step of the way.
Fans were quick to despise this more vengeful version of Robin. Although Jason was motivated by good intentions, he displayed a ruthlessness that was uncharacteristic of the Boy Wonder.
The Joker kept Jason in a sealed-off and abandoned wing of the asylum, tied to a chair. There, with Frank Boles covering for him, Joker tortured and brainwashed the young man. As part of a psychological plan, Joker forced Jason into believing that Batman had abandoned him, and that Batman was the true villain.
Instead, Jason was kidnapped and beaten to death with a crowbar. Despite Batman's efforts, he's seconds too late to get to the scene, Jason being killed in an explosion of the warehouse following his torture by the Joker. Batman held Jason's dying body, watching his life slowly fade away.
Finally beginning to forgive the Dark Knight, Jason ultimately saved and freed Batman, when he was imprisoned within the ruins of Arkham Asylum, by disarming Scarecrow with his sniper rifle, at which point Batman subdued the villain with his own fear toxin and finally brought him into custody.
After Batman caught Jason attempting to steal the tires of the Batmobile. Upon quickly discovering the boy doesn't have a family and has succumbed to resourcefully making a way for himself on the street, Batman takes Jason Todd in as one of his own.
Tim Drake Debuted as Robin Two Years After Jason Todd's Death. Tim eventually made his way to a still-grieving Bruce and proved himself worthy of the Robin mantle, donning his suit and aiding Batman against Two-Face in Batman #442 (by Marv Wolfman and Jim Aparo).
Jason remained dead for six months, his legacy haunting Batman. However, when the evil-alternate reality Superman known as Superboy-Prime punched reality itself, the timeline stuttered, and Jason was restored to life. Jason broke out of his coffin, but collapsed from exhaustion in the cemetery.
It makes Bruce 22 years older than Jason (35yo when he adopts him), a more reasonable age gap for a parent and child, which plays into Bruce's more immediately parental relationship with Jason (and thus Dick's jealousy over it). It then makes Bruce 24 years older than Tim (37 after Jason's death and upon meeting Tim).
The truth is revealed that Harley Quinn herself was the one who unknowingly killed Nightwing, expressing her more violent side. A weird twist involves a potato clone inadvertently made by Jim Gordon, but Harley is still responsible for the murder.
Background. Robin was the protégé of Batman and aided him in combating crime in Gotham City. However, at some point before the Battle of Metropolis, the young vigilante was captured and later killed by the Joker, with the aid of his girlfriend Harley Quinn.
While fighting, Nightwing get sprayed by the fear toxin and goes crazy. He gets sliced by Scarecrow's scythe in the arm and before he can get impaled, Catwoman saves him.
After his resurrection, Jason was enraged that Batman hadn't avenged him by killing the Joker and that he was seemingly replaced by a third Robin in Tim Drake.
Red Hood's hatred towards Nightwing stems from Dick's efforts to emulate Batman and be the "good son." Internal monologues reveal Jason's jealousy towards Dick's pursuit of goodness, offering intriguing insights into his character.
A resurrected Jason, however, didn't see it that way and felt that Bruce not avenging him and allowing someone else to become Robin in his place meant that he never cared about him. To get back at Bruce, Jason becomes the Red Hood and started to kill criminals than handing them over to the police.
