When x-ray falls on an atom,the atom scatters it in all 4pi solid angles. In case of a crystal also the atoms sitting in different planes scatter light in all 4pi direction. But when it comes to Bragg equation, we always consider the forward direction only. Bragg equation can also be satisfied on all points of a circle which lies on an outer plane that is parallel to the crystal plane which is considered ie when the incident and reflected beams and the normal to the surface are not in same plane.
Yes, individual atoms scatter in all directions. But they add upp in phase when the scattered wave comes from a plane only for the specular direction.
The Bragg conditions is the next step, adding reflections from many planes with the same orientation and distance.
Crystals have many such planes in many directions. And in reality, of course, there are no planes that the atoms "sit on". There are just 3D arrays of scattering centers. One can understand Laue diffraction by considering the response of these scattering centers to a pulse (not a wave).