What the shit. How can a magnet and an old flashcard even do that? I don't understand anything. Please explain.
Because of a "feature" Nintendo introduced in the bootcode of every 2DS/3DS console (until now, at least) which executes a signed (or haxsigned) code from a "special" DSCart and NOT from NAND just after you turn on the device if the lid is closed and you press some keys. This makes possible to have control of the system at the lowest level even before any piece of software from NAND is executed... or if the NAND is bricked.