We tend to think of a discovery in terms of the power of the discovered piece rather than the discovering piece. Typical case: you sacrifice a knight with check that reveals an attack of the piece behind the knight, say a rook or a queen. The smothered mate discovery in this position has it the other way round: the knight is both discovering piece and the main attacker, while the discovered piece, the queen, is merely the “diversion”, forcing Black to move the queen rather than the rook. Once the queen has moved, Black can’t defend against both threats, smothered mate and losing the exchange. Source: “Seizing a Point” by Rolling Pawns.
While we’re on the topic of smothered mates, allow me a digression if I may: Remember the poke in Worms? The smothered mate is a bit like the poke in my opinion. It’s the bitch-slap among the mates. If you want to humiliate your opponent, the smothered mate is your weapon of choice. Of course, the smothered mate is also a magnificent triumph of space over material, and as such is a tribute to the beauty and depth of chess. Or something.