Flash droughts have become more frequent, yet their underlying mechanisms of such changes remain unclear. Using an explainable artificial intelligence–based clustering framework with reanalysis products and Earth system models, we show that the major driving mechanisms of global flash droughts have shifted from precipitation dominance to a compound effect of temperature, transpiration, and precipitation. This transition drives a surge in flash droughts over the past decade, with more rapidly developing, severe, and enduring soil droughts. Anthropogenic warming and vegetation greening are the main drivers of the observed surge. The transition, which has emerged beyond natural climate variability since 2017 and is mainly detected in Eurasia, Amazon, and Africa, exposes ~650 million people under threat and reduces gross primary productivity by 0.15 ± 0.1 petagrams of carbon per year. Our results demonstrate that biosphere and atmosphere responses to anthropogenic forcing have altered flash drought drivers, emphasizing the urgent need for targeted mitigation strategies.