[NERD]
In the pre "Crisis on Infinite Earths" time-line, Krypton was a techno-utopia. A society devoid of want or war. When Jor-El first discovered the impending cataclysm he was able to recruit a substantial group of followers who openly warned thier fellow kryptonians of what was coming as well as embarking on a privately funded program of starship construction to prepare for the evacuation. This came to an end when the shipyards, 90% of Jor-Els followers and a series of automated construction droids built by a time-travelling Kal-El were lost with the rest of Kandor when Brainiac stole Kryptons second largest city.
There was never any indication that the cataclysm itself was anything but a natural event compounded by Kryptons ruling science councils heads being planted firmly in the sand.
Following the cosmic upheaval created by the Crisis on Infinite Earths and the subsequent collapse of the multiverse, a new time-line established itself wherein Krypton was both environmentally and emotionally barren and the incredibly advanced technology of Krypton was used to sustain a society that had socially stagnated.
Several millenia prior to this, it had been a common practice on Krypton to sustain life through the use of clones. Three clones were grown and held in a permanent coma for every man, woman and child on Krypton . Replacement parts were taken as needed from the clones to extend kryptonian lifespans. This practice was vehemently opposed by a religious cult started by an travelling alien cleric who had come to krypton seeking converts. Around this time, one of Supermans ancestors, Kem-El, a man with visions of Kryptonians as a master race, had introduced a genetic marker into the population that rendered Kryptonians incapable of surviving outside Kryptons atmosphere.
A scandal that tore Kryptons social fabric apart occurred when a clone was "stolen" by it's owner from the organ bank and was allowed to grow and function as an individual even rising to prominence in the high society of Kryptonopolis. The news that a clone had achieved a full life utterly destroyed the claims by Kryptons ruling elite that all clones grown for organ and tissue transplants were permanently brain dead. This provoked the pro-clone faction into open warfare plunging Krypton into a civil war that would last for centuries. The opening broadside in the Kryptonian Clone War was fired by an ultra-radical clonie group calling itself "Black Zero". They detonated a nuclear weapon inside the city of Kandor killing 40 million Kryptonians.
The Kryptonian Clone Wars culminated in a raid on Black Zeros base of operations centuries later led by another Superman Ancestor, Van-El. By this time, Black Zero had determined that Kryptonians as a people were beyond saving and had constructed a doomsday device to be dropped into Kryptons core and detonated there destroying the planet. In the ensuing firefight with Van-Els forces, the device was damaged, though dropped into the core, it fizzled, sparing for a time the war torn planet and it's people.
By Jor-Els time, Krypton had decayed into a world like the Vulcan of "Star Trek" only without all the emotional instability. The planets surface never recovered form the devastation of the clone War and it's people isolated themselves from one another and shunned all emotional involvement. Jor-El had discovered the genetic flaw introduced by Kem-El and corrected it in his yet unborn son and had discovered as well the source of the green radiation that had been killing Kryptonians in droves. While Black Zeros doomsday device had fizzled centuries earlier, it set off a chain reaction in Kryptons core that was going to do what Black Zero had originally intended it to do... destroy the planet Krypton. But these discoveries came to late to save anyone but Kal-El.
In this time-line, the destruction of both the planet krypton and the genetic flaw which prohibited any attempt to save her people were both very much MIHOP scenarios.
This time-line was all but erased following the "Zero Hour" event wherein the first human member of the Green Lantern Corps, Hal Jordan, while possessed and influenced by the alien entity "Parrallax" attempted to start a new "Big Bang" and create all of history anew in order to restore Hal Jordans beloved Coast City and his family which had been destroyed years before by the alien warlord Mongul.
In the new time-line, as retold in "Superman: Birthright", the original Krypton as a society at the zenith of its technological, social and spiritual development reasserted itself. And the disaster that befell them was once again a purely natural one.
This time-line too is rumored to have been re-written by the reality altering events of the recent Infinite Crisis, or by the upcoming Final Crisis.
Wether the "newest" Krypton was destroyed by MIHOP remains to be revealed.
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