They tend to give out reveal copies early apparently:
Games likw SM3DW and DKCTR had sudden huge marketing blowouts 1-2 months before launch. That pre-release media showed off some of the best parts of those games which got people interested who otherwise weren't by previous trailers, even though I was concerned about spoiling myself.
I wasn't expecting them to reveal what seems like everything with MK8, but the game looks so good I can't resist watching everything (gives me a slight advantage learning track layouts early too

). Though I think they could've picked some really good tracks/characters to release footage of instead of revealing them all. Maybe there's more hidden, who knows, with it out there now it could leak anytime.
All the recent MK8 blowouts have surely got more people's attention, so maybe it'll help them in the end.