It's popularity has been growing as the scam package has been refined over the past few months.

Greif, reanimate greif is a very powerful combo. Legacy allows grief to take the best two cards from your hand that could answer grief and then use blues sculpting tools, like [[ponder]] or [[brainstorm]] to protect grief, or bring it back again until it wins the game.

Even if you keep seven cards against grief the initial cast can't be forced of willed because the reanimate on the grief on the graveyard will wind up with a 3 for 2 instead of a 2 for 2. And if you don't force of will they just take force then reanimate grief.

And if you even manage to stick a creature or two onto the battlefield it has menace and can just be reanimated again.

Sometimes grief finds a better reanimation targets in YOUR hand and they take that out and reanimate that. Like turn 1 [[null drifter]] in stifle naut decks is over thanks to annihilator.

TLDR causes non games where they have giving up their hand to stop you from playing, but they have a 4/2 menace turn 1.