Why would China do something stupid and build so many nukes if they don't have any additional benefit because of the second strike doctrine effectively negating nuclear war.
The destructive area increase for a larger nuke is only marginal in comparison to the increase of explosive power.
Destruction is roughly on a 2 dimensional surface while the explosive power projects energy into 3 dimensions.
A thousand times more power gives a ten times larger radius and a hundred times more destroyed surface, but you could achieve the same destroyed surface with 100 tactical nukes with the power value 1 instead of 1000 each and a combined yield of 100. That's the reason why there is cluster munition after all. Instead of increasing raw power, much more could be derived from controlling and directing the energy of specified characteristics. Conventional weapons will increasingly close the gap to tactical nukes and a number of tactical nukes or a capable replacement of these can achieve the same as giant single nukes at a fraction of the costs.
Small nukes have a
and each needs an infrastucture for reliably kickstarting the spallation process that is difficult to create, but still need much less fissile material if combined for the same effect.
Larger nukes have the problem with gravity that atmospheric pressure is ever lower high above, making an increasing part of shockwave energy go into creating a
(that is not limited to nukes).
The most cost efficient application of nukes are mid sized nukes within the regime of good efficiency with multiple warheads in one highly developed missile. Gigantism is a sign of mental retardation because the creators lack the ability to use pocket calculators for cost efficiency. Strategic nuclear weapons are second strike tools. Tactical nukes by contrast are first strike tools as part of the nuclear escalation. Publishing nuke numbers was meant to end the arms race of the Cold War in which China wisely didn't participate. The demands for China's nuclear arsenal are credible minimum deterence (that doesn't require a
except to compensate for dissatisfaction with penis length and the aforementioned mathematical abilities) that might require some increases in missile number, sophistication and numbers of very
strategic warheads as well as a few tactical nuclear devices for special strikes like neutron bombing, EMP, carrier-killing and suitcase nukes for asssassins if all other methods fail.
Nukes are the most expensive weapons that constantly drain lots of money from conventional armament and are unlikely to be really used against a similar armed enemy as old chairman Mao explained. The more nukes you have, the less likely you are to win the non-nuclear and non-territorial wars of the future.
Its how effective the execution is 
