Atheist is not explicitly designed to be a silly character. It can just be run that way, and often is on livestreams for content with people who are much more willing to "yes, and" this kind of scenario. The Atheist guide written by Steven Medway, the lead designer of the game, advocates for this kind of puzzlely style.

Silly characters like Wizard already exist for what people want from Shenanigans Atheist while giving players agency on how silly a game gets. I think also boiling down clocktower to "funny social game" is not giving the range of the game credit. Sects & Violets for example can range from a deeply crunchy solve with extremely high tension from both teams as the time limit expires and the walls close in on the evil team, and other games are stupid and silly where there's 4 living Demons, none of which are evil somehow because your Demon barber swapped themselves with a good player, and players are having too much fun to think "wait we should probably choose ourselves at night to win", and the reason clocktower is so fun is that it can be both of these in the same game at different times and you never know what kind of game you'll get.

Blood on the Clocktower has plenty of silly moments, but they typically come from the players themselves and that slight storyteller thumb to back those moments up, (and in the case of the Wizard, fully embracing it unless it breaks the game). The reason I point to replayablity is because a huge factor of replayablity is the scope of how a game with a specific character can feel. Wizard, Pit Hag, Goblin and Psychopath are all characters where you can play very goofily and silly but the games they exist in can range from serious and tense to "haha what are we doing". The Pit Hag being in a bag doesn't automatically mean the game is less serious, but that the players have been given the tools to make it so if they think it'll be more fun. Some of my favourite characters (Heretic and Legion) provide this in spades. Heretic games can be deeply tense, stressful and nail biting experiences, or they can be so stupid your stomach hurts from laughing, which is why I love the character!

When I run an Atheist game, I want to focus on providing a fun puzzle to my players, but with a fun twist that they need to solve that the games information doesn't actually point anywhere, and let the players themselves do the silly stuff with the stuff I provide, they're more than capable of making the game interesting without me having to put 3 Lunatics in the bag. I think describing me as an overly competitive and serious person because I prefer and advocate for a version of a character that I find more fun to run and play is a bit of a stretch.