Dry conifer forests of the Southern Rocky Mountains have co-evolved with fire as a natural disturbance and an essential process in forest succession. However, recent increases in fire size, frequency, and severity have pushed these ecosystems outside of their natural range of recovery with increased post-fire regeneration failure, raising concerns about long-term forest resilience, carbon storage, and ecosystem service provision. Prior studies have identified that early regeneration failure was found to be a key mechanism underlying this pattern, particularly during the earliest stages of establishment when seeds must successfully germinate and survive their first few years. However, the ecological drivers that determine seedlings establishment and persistence during this critical early period remain poorly understood. In this study, we evaluated the drivers of seedling establishment and the abundance using state-of-the art high resolution Uncrewed Aerial System (UAS) surveys across ~25 burn scars covering over 200 hectares of Ponderosa pine dominant forests in the Southern Rockies ecoregion. Applying Bayesian regression models over 230,000 individual detections of seedlings, shrubs, mature, and dead trees, we found that seedling establishment (presence) was primarily driven by topography, vegetation legacies and postfire climate conditions, with strong positive effects of deciduous cover, pre-fire vegetation cover, and shrub density. Higher elevations and high-severity fire interactions reduced establishment probability. In contrast, seedling abundance once established was more strongly influenced by structural and dispersal factors, particularly proximity to mature trees, shrub density, and dead tree presence. Together, these results indicate that postfire regeneration operates as a two-stage process, where legacy vegetation and climate control initial establishment, while seed availability and microsite structure regulate long-term seedling density. Overall, our findings suggest that postfire forest recovery depends on maintaining forest legacies and favorable climate conditions during early recovery. From a management perspective, this implies that retaining seed trees, protecting surviving patches, or targeted replanting in isolated high-severity areas could help prevent long-term forest loss followed by transitions into shrubland or grassland.