In 2021, the Glasgow Financial Alliance for Net Zero (GFANZ), an umbrella organization mobilizing a network of sectoral initiatives for climate action, was launched to ‘transform the global financial system.’ In part due to its efforts, hundreds of global financial companies joined and collectively committed to net-zero emissions reduction targets. But the momentum was short-lived: in the ensuing years, internal and external challenges led to defections, the reconfiguration of GFANZ, and the collapse of affiliate alliances. Such a pattern rests uneasily with theories of change like the norm cascade, which asserts that exponential uptake is a prelude to resilience, not fragility. In this paper, I argue that cases such as GFANZ may be better described as a ‘hype cycle’ rather than a norm cascade, where ambiguity and uncertainty limit normative and calculative reasoning; actors refer to each other’s behavior as an indication of what to do; and time limits incentivize participation to avoid being left behind. I demonstrate the validity of this account through an analysis of three GFANZ-affiliated alliances (the Net-Zero Insurance Alliance, the Net-Zero Banking Alliance, and the Net Zero Asset Managers Initiative), and their episodes of membership growth and decline.