For anyone wondering about a "blast crater", just watch a Blue Origin crew capsule landing on earth. That vehicle uses retrorockets, just like the moon lander, and never leaves any kind of noticeable crater. Therefore, I don't see why we should expect to see one on the moon.
The Blue system uses parachutes but the moon deceleration is much slower (takes place over a long period of time). The actual impact on the surface is probably comparable. The capsules are relatively lightweight so the retrorockets aren't actually particularly powerful. It would take too much heavy propellant to make them powerful.