Warning: SPOILERS ahead for the midseason finale of Riverdale
After nine episodes of terror on Riverdale the identity of The Black Hood has been revealed, and after so much build-up it's... kind of a disappointment. After all this time and speculation about the different main characters who might be suspects, it turns out that the janitor did it. Yes, the Black Hood was Joe Svenson - a character that audiences had only met a couple of episodes prior. Showrunner Roberto Aguirre-Sacasa has explained why Svenson was chosen, and while some of the logic is sound, it did not really work in execution.
Many of the theories about who the Black Hood would turn out to be were centered around characters who were already known to audiences, like Hal Cooper and Sheriff Keller. Based on what little of him could be seen through the hood's eye holes, it was clear that he was an older white man with green eyes. Svenson might be an older white man, but he does not fit the physicality of the imposing Black Hood, and their eyes don't match at all.
The real problem, however, is that Svenson's introduction was rushed. He was portrayed as creepy and suspicious almost from the moment he was introduced - in contrast to his goofiness in the comics - and in spite of the detailed backstory provided, Svenson simply has not been around nearly long enough for audiences to care about him.
A Recap of The Black Hood's Crimes
The Black Hood was first introduced in the season 1 finale, when he appeared to be a simple robber who came into Pop's. Instead of stealing anything, he shot Fred Andrews in cold blood. Archie raced his father to the hospital and got him there in time to save Fred's life, but the Black Hood was far from done. He traveled to nearby Greendale and murdered Miss Grundy, convincing Archie that the people he cared about were the killer's targets.
The next time the Black Hood attacked, he shot at Northside High students Moose and Midge while they were parked and doing jingle jangle. They survived, with Moose using his bulk to protect Midge. Eventually, the Black Hood revealed his true intentions to Alice Cooper: he was punishing the town's sinners. Further contact with Betty included his admission that her speech at the town Jubilee was what inspired his killing spree. He began to psychologically torture Betty by forcing her to publicly humiliate her mother, end her friendship with Veronica, break up with Jughead, and name the next potential victim. Finally, the Black Hood forced Betty to help him find a local drug dealer known as The Sugerman. Betty succeeded, but attempted to thwart the Black Hood by having The Sugarman arrested - to no avail. The Black Hood broke into the jail and murdered him in his cell.
In the midseason finale, Betty and Archie became worried about Svenson when he was absent from school. After a visit to his home turned up nothing (and Betty received a finger in a box from the Black Hood) she and Archie were convinced that Svenson might be the killer's latest victim. A phone call from the Black Hood gave them the chance to save Svenson if they could find the location of the town's primal sin - forcing them to dig deeper into Svenson's past.
Already they knew that Svenson was really Joe Conway, who as a child survived when his parents and siblings were brutally murdered by a killer known as the Riverdale Reaper. Young Conway had named a traveling preacher as the killer, and a number of townsfolk had murdered the man in an act of vigilante justice. But their research brought even more to light, as Betty and Archie learned that Conway was not sure he named the right person.
Further research revealed that Betty's grandfather had been part of the group who killed the alleged Reaper. A little more investigation brought Betty and Archie to the site where the man had been killed so many years ago. Instead of finding Svenson, Betty and Archie were held at gunpoint by the Black Hood, who tried to force Betty to bury Archie alive. But Betty was able to fight back and the teenagers cornered the killer with his own gun until Sheriff Keller arrived and killed the Black Hood. Off came the mask, to reveal that it was Svenson all along.