force from acceleration scales linearly with mass. mass, however, scales cubic with size: something at 1/10 scale is 1/1000 the mass.
surface scales square with scale (something at 1/10 scale has 1/100 surface or cross section surface)
with miniaturization with factor x you get 1/x^3 mass and 1/x^2 cross section surface. as a result stresses (Force/Surface) becomes 1/x less on a given surface for acceleration.
(on mobile, edited a few times)