a) they weren't targeting the industry, but the civilian population...
b) not that much
The use of firebombs were not used for the sake of destroying the industrial complexes, but for like reccejet said, psychological effect but also the horrible effectiveness it has of putting cities on fire, which is a nightmare for any city even today, not just from a psychologically point of few. Especially when your city is not just all-concrete buildings. The strategic bombing of cities alone has a huge effect on the functioning of a nation and thus ability to sustain its war efforts and support for the regime/war, but using ammunitions like this you are clearly trying to kill masses of civilians, in the most traumatizing way possible until the advent of the nuclear bomb I guess. Makes you think some more of the definition of 'total war' and strategical bombing of densely populated cities.
Cluster bomb subminitions are used to bomb a certain area, they can either detonate when they hit the ground, or bury themselves and act as mines, waiting for a trigger to explode. A very effective weapon when you want to take out troop or soft target concentrations, or in case of mines put runways or roads out of use. As you can imagine, these small mines are quite a problem to clean up, even when the war is over. Several nations signed a treaty to ban the use of cluster bomb containing mines. However the subminitions can also be incendiaries.
The 'firebomb' used by the US in the second world war, was a container, clustering 38 M-69 firebombs. Each M-69 weighed only 2.3 kilograms (6.2 pounds). Quite sophisticated for its time:
The aimable cluster was a bundle of M-69s fitted with a nose shroud and tail assembly. It was dropped from high altitude and then broke apart at about 900 meters (2,000 feet), scattering its M-69s. Each M-69 then ejected a long strip of cloth to stabilize itself, and crashed nose-first into buildings below. On impact, it ignited its payload of napalm, which shot out of the tail of the bomb in a burning jet. Under optimum conditions, this jet could travel 45 meters (150 feet).
http://www.vectorsite.net/twbomb1.htmlOne night of firebombing Tokyo took more casualties than Nagasaki and more than half the number of Hiroshima...