Key word art. Artwork outside the game. Bonus content. The game itself is presented with relative seriousness.
And do remember that Classic Castlevania was not always so "serious". It was serious in tone, but was always sort of a tongue in cheek reference to classic horror movies and shit. Simon Belmont was a barbarian for petes sake. Cant quite consider that serious. Bloodlines is where it started to get SRS BSNS, and SoTN cemented that serious style, which continued till OoE. Although again, PoR was a total Joke, DoS with it's pitfalls of Hammer's love troubles was still more serious.
Rondo sort of does the same "this is a B movie" thing, and instead makes it "this is a cheap 90's action anime OVA"
You've got Richter chowing down on a massive piece of meat
because wallmeat in Castlevania is totally a serious thing right? It's been ridiculous since day 1.