  Moir\'e structures, along with line-graph-based $d$-electron systems,
represent a setting to realize flat bands. One form of the associated strong
correlation physics is the Kondo effect. Here, we address the recently observed
Kondo-driven heavy fermion state and its destruction in AB-stacked
hetero-bilayer transition metal dichalcogenides, which can be controlled by the
gate voltages. By studying an effective interacting Hamiltonian using the slave
spin approach, we obtained a phase diagram with the total filling factor and
the displacement field strength as the tunable parameters. In an extended range
of the tunable displacement field, our numerical results show that the relative
filling of the $d$ orbital, which is associated with the highest moir\'e band
from the $\rm MoTe_2$ layer, is enforced to be $\nu_d \approx 1$ by the
interaction. This agrees with the experimental observation. We also argue that
the observed high coherence temperature scale could be explained by the
non-negligible bandwidth of the $d$ orbital. Our results set the stage to
address the amplified quantum fluctuations that the Kondo effect may produce in
these structures and new regimes that the systems open up for Kondo-destruction
quantum criticality.
