When overstressed as a whole with uniform exterior/interior pressures, the fuselage has breakaway points that are designed to allow the plane to remain in flight after the overpressure is explosively released. The structure adjacent to these points is reinforced and designed to keep the plane structurally intact and relatively controllable at a designed airspeed. You can see in this photo how the break was relatively symmetrical with respect to two axes, balancing the forces. It was also opposite the tail control surfaces and this would allow the greatest possible leverage to keep the plane level against the forces generated by this break. If the moment (force X distance from axis) generated by an aerodynamic disturbance is greater than the maximum moment from a fully deflected control surface, you lose control in that axis.
A bomb creates a local pressure at a random or specifically selected point. The break is unlikely to be symmetrical or surrounded by reinforcement. The holes created by the Lockerbie bomb were far smaller than on this flight, but proved instantly catastrophic.