The answer is a combination of product strategy and what could be called the lottery ticket effect
The real-world version is much tamer, forcing the player to banish all cards in their hand to draw 2 and isn't worth the trouble unless players are using a deck solely focused around banishing cards like Gren Maju Da Eiza
How much does Fiend's Sanctuary cost
There isnt a real-life problem that nature hasnt solved for us already, and it turns out reproduction is one of the best ways to increase shiny rates when Shiny hunting
This is an extremely expensive spell that drops in price once things start dying, replacing your hand with eight cards and dealing eight damage to each opponent
Remie didn't play a lot of green cards in his main deck or anything, he just realized that as long as a RW deck is already willing to play Bloodstained Mire, Flooded Strand, Windswept Heath, and Wooded Foothills (as Tsapko's straight RW was), it might as well get paid off