Complex sentence: In each case, only the detonator caps fired and the bombs themselves did not go off, this may have been due to the low quality hydrogen peroxide used in the devices, which had been obtained from a large number of easily available sources.
Split into simpler sentences: In each case, only the detonator caps fired and the bombs themselves did not go off. This fortuitous "dudding" of four simultaneous attempted bombings may have been due to the low quality hydrogen peroxide used in the devices, which had been obtained from a large number of readily available sources.