Nuclear fusion requires both compression and heating of the fuel. In nuclear weapons, this is accomplished with a combination of radiation pressure and a fissile sparkplug, respectively. In inertial confinement fusion, there are two distinct laser pulses with different characteristics. A fusion pellet detonating would release radiation that could compress another pellet, but there would be no method of heating that pellet at the appropriate moment.

There may be an engineering method to overcome this, but it would be way beyond the difficulty of getting that first pellet to ignite, which already is a bleeding edge technological development.