What destroyed Praxis in Star Trek Into Darkness?

Question

In Star Trek Into Darkness (STID), we see the Klingon homeworld of Kronos, and its moon. The moon is essentially destroyed; it orbits Kronos in large pieces of its former self.

A recent answer reminded me that in the film Star Trek VI: The Undiscovered Country, Qo'noS' moon Praxis is destroyed. Admittedly, these are two separate timelines, but the destruction of the moon in ST6 takes place long after the timeframe depicted in STID. This suggests a different catastrophe caused the destruction of Praxis in STID.

What caused the destruction of Praxis in Star Trek Into Darkness?

Answer 1

In canon sources, what caused the destruction is left unspecified.

The movie's co-writer Alex Kurtzman also stated that what exactly the moon was was meant to be left unspecified - that it might not actually be Praxis. That said, it was identified on the viewscreens as Praxis, and the novelization further makes it explicit.

According to the comic prequel Star Trek: Khan, while he was still known as John Harrison one of his missions in Section 31 was to destroy Praxis.

Memory Beta further expands on this:

It was later revealed that Section 31, under orders from Starfleet Command CO Admiral Alexander Marcus, authorized a 2 missions; The first mission was to just destroy the facilities. However, the squad's ship was detected and Lt John Harrison was captured. In the Second mission "John Harrison" used a personal transporter to beam in alone. There, Harrison took out the Klingon guards, planted demolition charges, and then beamed down to the Ketha Province on Qo'noS. Praxis was then destroyed. (TOS - Khan comic: "Issue 4")

Answer 2

After the USS Kelvin kamikazed the Narada, the Romulan ship was disabled. A group of Klingon Warbirds was near by and captured the Narada shortly after it destroyed the Kelvin. Nero and a unknown number of his crew was sent to the Klingon prison planet. The top of Nero's ear was cut off somehow before him and his XO escaped. Somehow they took back the Narada from the Klingon's and Uhura monitored a transmission that 47 klingon Warbirds was destroyed by the massive Romulan ship. It is possible that Nero destroyed Praxis with the Red matter for punishment for their capture. More than likely Nero did not want to completely destroy the Klingon's because he knew the past, and they were not friendly to the Federation. Thus he wanted to weaken them as to not be as much of a threat to the new timeline Romulans, but leave them around to help destroy what was left of the federation if Nero would have succeeded destroying Earth. That would explain why the Narada only destroyed Praxis and not Kronos.