The folks over at Wizards of the Coast have been setting new precedents in Magic: The Gathering this year. After the most recent Core Set hit MTG: Arena, the devs took a more active role in shaping the meta.
The reason for the more immediate changes to card legality is the more immediate, obvious nature of the meta. For along time, Magic: The Gathering was traditionally, primarily physical in nature. This means it took a wide survey of players and analysis of top level play to determine what constituted the meta. Now, with meta defining live tournaments canceled and a readily available digital platform, the meta is defined faster than ever. In the process, Wizards can quickly identify which cards are too powerful.
As a result, the meta of various formats became obvious very quickly, and a few key cards made themselves known. This led to Wizards banning several powerful cards in several formats, foremost among them Inverter of Truth and Cauldron Familiar. Now, after just one week of Zendikar Rising rotating into physical play, Wizards has brought down the banhammer again. This time only one card was targeted: the Mythic Rare Uro, Titan of Nature's Wrath is now banned in Standard format.
The reason for the ban is readily apparent to anyone playing highl level MTG. Introduced in Theros: Beyond Death, Uro quickly grew to dominate the meta. Although sacrificed as soon as it hits the board, it still heals, draws a card, and plays an extra land for a cool three mana. Then, for only one mana more and five cards exiled from the grave, it returns, uses its effect again, and this time, it stays. The winning deck of the first Historic format MTG tournament used four copies of Uro as one of only two creatures in the deck, and it's not hard to see why.
Wizards has stated it wanted to wait until after the Standard rotation to decide on what action to take. The reasoning was that the shuffle associated with a set rotation may have been enough to shake off Uro's dominance. It was not, and so now the Fall 2020 Standard Rotation comes with the added banning of Uro for the foreseeable future.
It's not like there weren't plenty of new cards to try out against the Titan. Zendikar Rising brings new cards and mechanics to the game, several of which are quite powerful. Unfortunately, several of these, including the returning Lotus Cobra and a new version of Omnath synergized too well with Uro. For now, Uro is back in the Underworld.
Source: Wizards