The James Webb Space Telescope (JWST) has discovered numerous massive black holes (BHs) in faint, broad-line active galactic nuclei (AGNs), known as "little red dots" (LRDs). These LRDs are more abundant than X-ray selected AGNs and are characterized by moderate dust obscuration. The BH accretion rate density inferred from their luminosity function is significantly higher than that from other AGN surveys. This suggests that the cosmic growth rate of BHs in this population does not decrease but increases at higher redshifts beyond z ~ 6. The radiative efficiency of BHs must be doubled from the canonical 10% value to align the cumulative mass density accreted to BHs with the observed BH mass density at z ~ 4-5. This indicates that most BHs in LRDs have rapid spins, with 96% of the maximum limit, maintained by prolonged mass accretion rather than chaotic accretion. The analysis also sets an upper bound for the stellar mass of galaxies hosting these LRDs, consistent with the standard cosmological model. The BH-to-galaxy mass ratio in LRDs exceeds the typical value in the nearby universe and aligns with that for JWST-detected unobscured AGNs. The dust-rich environments in LRDs are proposed to facilitate the emergence of rapidly spinning and overmassive BH populations during the epoch of reionization. This scenario predicts a potential association between relativistic jets and other high-energy phenomena with overmassive BHs in the early universe. The study also highlights the importance of considering the AGN luminosity estimates, noting that different methods can lead to significant variations in bolometric luminosity functions. The analysis suggests that the majority of early BH populations in dust-rich environments exhibit high spins, indicating that BH growth is likely dominated by prolonged accretion episodes with coherent angular momentum. Future gravitational-wave observations with space-based detectors like LISA, TianQin, and Taiji could directly test these conclusions. The study also discusses the implications for BH growth mechanisms at z > 5, emphasizing the role of prolonged accretion and the potential for high spins in early BH populations.The James Webb Space Telescope (JWST) has discovered numerous massive black holes (BHs) in faint, broad-line active galactic nuclei (AGNs), known as "little red dots" (LRDs). These LRDs are more abundant than X-ray selected AGNs and are characterized by moderate dust obscuration. The BH accretion rate density inferred from their luminosity function is significantly higher than that from other AGN surveys. This suggests that the cosmic growth rate of BHs in this population does not decrease but increases at higher redshifts beyond z ~ 6. The radiative efficiency of BHs must be doubled from the canonical 10% value to align the cumulative mass density accreted to BHs with the observed BH mass density at z ~ 4-5. This indicates that most BHs in LRDs have rapid spins, with 96% of the maximum limit, maintained by prolonged mass accretion rather than chaotic accretion. The analysis also sets an upper bound for the stellar mass of galaxies hosting these LRDs, consistent with the standard cosmological model. The BH-to-galaxy mass ratio in LRDs exceeds the typical value in the nearby universe and aligns with that for JWST-detected unobscured AGNs. The dust-rich environments in LRDs are proposed to facilitate the emergence of rapidly spinning and overmassive BH populations during the epoch of reionization. This scenario predicts a potential association between relativistic jets and other high-energy phenomena with overmassive BHs in the early universe. The study also highlights the importance of considering the AGN luminosity estimates, noting that different methods can lead to significant variations in bolometric luminosity functions. The analysis suggests that the majority of early BH populations in dust-rich environments exhibit high spins, indicating that BH growth is likely dominated by prolonged accretion episodes with coherent angular momentum. Future gravitational-wave observations with space-based detectors like LISA, TianQin, and Taiji could directly test these conclusions. The study also discusses the implications for BH growth mechanisms at z > 5, emphasizing the role of prolonged accretion and the potential for high spins in early BH populations.