MDFCs were first introduced in Zendikar Rising and were used in the next two sets, Kaldheim and Strixhaven: School of Mages
Essentially a hastened Rummaging Goblin, you get access to madness costs on your spells with very little effort, with the main upside being that you will have a dedicated way to fill your graveyard with cards that want to be there, right from the command zone
Sure, the graveyard hate fuels the second ability, but the second ability also means youre taking advantage of other players who use exile
By avoiding the typical rotation model at least for now Pokmon TCG Pocket players dont have to worry about their cards becoming illegal and having to start fresh with a new deck
Its very much the kind of niche thing that the format allows for and to some extent encourages
Imotekh the Stormlord Imotekh is a great "lieutenant" to Szarekh for this deck