There were a lot of factors: figuring out what people wanted out of a D&D set, how to fit that into competitive play environments, and how to capture the essence of everything on the cards
Chart shows the price of Venonat [1st Edition] #11 at the end of each month going back as long as we have tracked the item.
Some have come and gone, while others, like EDH, otherwise known as Commander, have become such a force that they've dictated the release of entire sets dedicated to the format
Although the Pokmon GO TCG expansion features many beloved characters and Pokmon from the popular Niantic title, some cards in the set are more valuable than the others
By including a swath of card types in your deck, and having ways to smartly fill your graveyard, you can gain some pretty powerful benefits on your creatures and spells by hitting the four or more different card type requirement.
It's nearly unbelievable that, about a year ago, GameStop halted pre-orders of all Pokmon TCG products altogether.