Why would the game, when discovering a copy of Eruption draw about 5 or more eruptions before shuffling 3 into the deck? Draw 1 (one) copy, damage all opponents, shuffle 3, surely that is the correct definition of the card?
Drawing a number of the cast on drawn isn’t listed on the card - fix the card so it draws one then shuffles 3 into the deck like it’s described as doing, thanks.
One thing you should keep in mind is that Tiangulate does not discover a copy of a spell, it discovers the actual spell and draws it from the deck.
Eruption is a Casts When Drawn spell, which does as it’s described. However, it has a secondary effect where, if you draw it, you draw a new card. These draw effects continue to happen if you keep drawing more Eruptions, which have their own Casts When Drawn effects, until you draw a card that isn’t an Eruption, after which the Triangulate shuffle happens.
Your opponent just got lucky by having a bunch of them already shuffled in beforehand so they were the topmost cards of the deck before the shuffling happened.