Fire does not destroy the world in Revelation 20:9. Read it again.
"And they went up on the breadth of the earth, and compassed the camp of the saints about, and the beloved city: and fire came down from God out of heaven, and devoured them."
Fire only destroyed those who marched across the earth, nothing else.
The fire of 2 Peter 3 is here in Revelation 6:12-17; the Second Coming:
"And I beheld when he had opened the sixth seal, and, lo, there was a great earthquake; and the sun became black as sackcloth of hair, and the moon became as blood; And the stars of heaven fell unto the earth, even as a fig tree casteth her untimely figs, when she is shaken of a mighty wind. And the heaven departed as a scroll when it is rolled together; and every mountain and island were moved out of their places. And the kings of the earth, and the great men, and the rich men, and the chief captains, and the mighty men, and every bondman, and every free man, hid themselves in the dens and in the rocks of the mountains; And said to the mountains and rocks, Fall on us, and hide us from the face of him that sitteth on the throne, and from the wrath of the Lamb: For the great day of his wrath is come; and who shall be able to stand?"
Notice that no humans were consumed by fire, yet this is the time when all mankind's works are burned up. Heaven dissolves like a scroll being rolled up. All the stars come to earth. The only place to hide are in caves or under all the rubble. Only intense fires all over the earth can cause the sun and moon to appear that way.
"But the day of the Lord will come"
Jesus comes to earth to start the Day of the Lord. That day with the Lord known as the Millennial Reign.
"And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory."
They are hiding out like Revelation 6 declares, not consumed by fire, but mourning. Now back to your so called "second coming" where only humans are consumed by fire, and nothing else. This is two separate and unrelated events. They do not even have the same outcomes. One has all those humans being burned up, the other only man's works are burned up, no humans at all.