In this paper, we prove that the smooth cubic moments dissipate for the Hecke–Maass cusp forms, which gives a new case of the random wave conjecture. In fact, we can prove a polynomial decay for the smooth cubic moments, while for the smooth second moment (i.e. QUE) no rate of decay is known unconditionally for general Hecke–Maass cusp forms. The proof is based on various estimates of moments of central L-values. We prove the Lindelöf on average bound for the first moment of GL (3) × GL (2) L-functions in short intervals of the subconvexity strength length, and the convexity strength upper bound for the mixed moment of GL (2) and the triple product L-functions. In particular, we prove new subconvexity bounds of certain GL (3) × GL (2) L-functions.