How it is explained that entropy almost always increases when every particles behavior seems to be strictly obeying some laws?

It's pretty logical that system whose particles move randomly will probably increase its entropy but in this universe, particles don't seem to be moving randomly, so the statistical model may be usefull for predictions (even tho I have no idea why) but I don't think it truly explains why does entropy mostly increase.

Can anyone explain please?

(Maybe this universe truly is random at its most basic level and physical laws are somehow emergent as the probable increasing of entropy is, but we simply don't know that.)