This card's [All Turns] effect prevents other effects from deleting this Digimon or returning it to its owner's hand or deck, so it isn't treated as being deleted by the game rules.
The card is also one of the most annoying to go up against because of its Oceanic Curse ability
Decks that used to be competitive, but have fallen by the wayside as cEDH evolved - With rules changes, banlist updates (for example Arcum Dagsson after the Paradox Engine ban), new cards being released, and people getting better at the game, the landscape of cEDH continues to evolve
as the inherent multiplayer play and politics unsure that these cards get to see their full potential
We can certainly attribute Shark Typhoons popularity to the current Standard metagame midrange decks are everywhere, and this is a fantastic midrange card but lets not ignore the power of this card
The First Turtle-Beast Level 4 WATER Reptile ATK 0/DEF 2100 You can Special Summon this card from your hand if your opponent Special Summoned a monster on their previous turn