  Recently, superconductivity was discovered at very low densities in slightly
misaligned graphene multilayers. Surprisingly, despite extremely low electronic
density (about $10^{-4}$ electrons per unit cell), these systems realize
strong-coupling superconductivity, with the transition temperature being a
large fraction of the Fermi energy ($T_c\sim 0.1 \epsilon_F$). Here we propose
a qualitative explanation for this remarkable phenomenon, highlighting
similarities and qualitative differences with the conventional uniform
high-density superconductivity. Most importantly, we find that periodic
superimposed potential generically enhances local interactions relative to
nonlocal (for instance, Coulomb) interactions. In addition, the density of
states is enhanced as well, exponentially in modulation strength for low lying
bands in some cases. Combination of these two effects makes moir\'e systems
natural intermediate or strong-coupled superconductors, with potential for very
high transition temperatures.
