They do nothing against mono color decks unless Richard is building the manabase, but against multicolor decks they can often be free wins and are definitely the highest win % cards for their mana values
I also like the way it incorporates its preevolutions, with Ralts, Kirlia, and regular Gardevoir
Its hard to say exactly why this card is performing so well, but the most likely answer is how rare it is to see a Shiny Pikachu
Spectacular ShowdownSpectacular Showdown is very similar in that you need your opponents to have a board when you play it, it's expensive and if it doesn't win you the game it leaves one of your opponents with a board full of double strikers
A big beater for control strategies that also nips cards from graveyards that it turns into food, it has all the elements you want as a one-of in a deck that plays these colors
There are 40 total reprints included on The List for Murders at Karlov Manor