  We propose a phenomenological understanding of the recently discovered weak
Mott insulator in the moir\'e superlattice of twisted bilayer graphene,
especially the emergent superconductivity at low temperature within the weak
Mott insulator phase, namely while lowering temperature, the longitudinal
resistivity first grows below temperature $T_m$, but then rapidly drops to zero
at even lower temperature $T_c$. An emergent superconductor in an insulator
phase is very unusual. Here we propose that this phenomenon is due to the pure
two-dimensional nature of the bilayer graphene moir\'e superlattice. We also
compare our results with other theories proposed so far.
