Was there any other working pod found on Eden Prime bunker? I mean, Why was he the only one preserved?
There were thousands of pods on Ilos in the the Conduit, which was a Prothean research centre.
Quoting the Mass Effect wiki
When the Citadel was attacked, the Conduit shut down to avoid detection & went into stasis, to be monitored by Vigil.
Since Vigil's power supplies began running low, and the cryo pods were in danger of failing, Vigil began cutting power to the pods of non-essential staff to conserve energy. When the Reapers finally withdrew through the Citadel relay, only the top researchers — a dozen individuals — were left. Vigil woke them, and the scientists pieced together what had happened.
The surviving Prothean scientists knew that rescue was unlikely.
Instead, they chose to protect the races they had been studying,
spared destruction due to their lack of advancement, and began working
out where the Reapers had come from, and how. After decades of study,
they worked out the connection between the Reapers, the Citadel, and
the keepers, and discovered a way to interfere with the signal that
compels the keepers to activate the Citadel relay.
Using the Conduit, the Prothean scientists left Ilos, travelled to the
Citadel and altered this signal. Their intention was to prevent the
Reapers from opening the Citadel relay again, and trap them in dark
space, but they had no way to be certain their plan had succeeded. The
fate of these Prothean scientists is unknown. As the Conduit portal
only links one way and there was no food or water left on the Citadel,
Vigil hypothesized they eventually starved to death.
Also, there were nearly one million Prothean warriors lead by Javik, stored in cryogenic lifepods in a bunker facility on Eden Prime.
However, before the facility could be sealed, traitors leaked its existence to the Reapers. Hundreds of thousands of stasis pods were destroyed in the attack on the facility, killing their occupants. To preserve the few remaining survivors, the facility's VI, Victory, initiated a neutron bombardment to purge Reaper forces. The bombardment also severely damaged the facility and rendered the systems responsible for automatically awakening the Protheans from stasis inoperable. As Javik's survival was a priority, Victory was forced to divert power from the remaining stasis pods to keep Javik's pod working as long as possible in the hope that future civilizations would discover it and revive him.