Diversity in Hydrogen-rich Envelope Mass of Type II Supernovae. (III). The mass-loss and evolutionary pathways of the red supergiant progenitors

We present a comprehensive analysis of 32 type II supernovae (SNe II) with plateau phase photometry and late phase ($nebular$) spectroscopy available, aiming to bridge the gap between the surface and core of their red supergiant (RSG) progenitors. Using \texttt{MESA}\,+\texttt{STELLA}, we compute an extensive grid of SN II light curve models originating from RSG with effective temperatures $T_{\rm eff}$ around 3650\,K and hydrogen-rich envelopes artificially stripped to varying degrees. These models are then used to derive the hydrogen-rich envelope masses $M_{\rm Henv}$ for SNe II from their plateau phase light curves. Nebular spectroscopy further constrains the progenitor RSG's luminosity log\,$L_{\rm prog}$, and is employed to remove the degeneracies in light curve modeling. The comparison between log\,$L_{\rm prog}$-$M_{\rm Henv}$ reveals that $M_{\rm Henv}$ spans a broad range at the same log\,$L_{\rm prog}$, and almost all SNe II have lower $M_{\rm Henv}$ than the prediction of the default stellar wind models. We explore alternative wind prescriptions, binary evolution models, and the possibility of more compact RSG progenitors. Although binary interaction offers a compelling explanation for the non-monotonicity and large scatter in the log\,$L_{\rm prog}$-$M_{\rm Henv}$ relation, the high occurrence rate of partially-stripped RSGs cannot be accounted for by stable binary mass transfer alone without fine-tuned orbital parameters. This highlights that, despite being the most commonly observed class of core-collapse SNe, SNe II likely originate from a variety of mass-loss histories and evolutionary pathways that are more diverse and complex than typically assumed in standard stellar evolution models.