The traps were just volcanoes, nothing more.
Just a plume volcano pushing deep basaltic magma from deep below the crust on such amounts as to cover an area exponentially larger than Europe with a kilometer thick lava flow and accompanied by very explosive rhyolitic eruptions. It put out one and a half billion tons of SO2 yearly (not to mention CO2). It was estimated to be a crack in the earth, at times, one thousand miles in length. But yeah, just a volcano.