  In contrast to prevailing knowledge, Ram\'irez Reyes and Yang (2021) showed
that tropical cyclones (TCs) can form spontaneously without moisture-radiation
and surface-flux feedbacks in a cloud-resolving model (CRM) simulation. Here we
ask, why? Thirteen 3D cloud-resolving simulations show that the
moisture-convection (MC) feedback can effectively lead to spontaneous TC
genesis and intensification in the absence of radiative and surface-flux
feedbacks. In the MC feedback, a moister environment favors new deep convective
events that further moisten the environment, leading to aggregation of deep
convection. The impact of the MC feedback on TC genesis and intensification
occurs in two distinct time scales: a short time scale set by detrainment
moistening the environment (a few hours) and a long time scale (17 days) due to
subsidence drying. The hours-long time scale of detrainment suggests that the
MC feedback is an efficient process relevant to TC genesis in the real world.
