All the "monad tutorials" are utter crap. Esp. the one with the burritos in spacesuits. All you need to know is that a monad is a monoid in the category of endo

All the "monad tutorials" are utter crap. Esp. the one with the burritos in spacesuits. All you need to know is that a monad is a monoid in the category of endofunctors and it all comes naturally from there.