Mat. 24:3 Now as He sat on the Mount of Olives, the disciples came to Him privately, saying, “Tell us, when will these things be? And what will be the sign of Your coming, and of the end of the age?”
If the disciples expected a sudden & glorious coming, why ask about a sign? In the context, they were asking about the destruction. Jesus has a lot to explain.
Jesus warns about the tribulation before the destruction. He's telling the Christians the signs they will watch for in order to flee the city.
26 “Therefore if they say to you, ‘Look, He is in the desert!’ do not go out; or ‘Look, He is in the inner rooms!’ do not believe it. 27 For as the lightning comes from the east and flashes to the west, so also will the coming of the Son of Man be. 28 For wherever the carcass is, there the eagles will be gathered together.
There will be a beginning of the final war. When it begins, the Roman legions - like vultures - will gather. The beginning will be unmistakable, like a flash of lightning begins the thunderstorm. The lightning announces the gathering of the legions intent on spoil.
But even that is not the end, there's more to come -
29 “Immediately after the tribulation of those days the sun will be darkened, and the moon will not give its light; the stars will fall from heaven, and the powers of the heavens will be shaken. 30 Then the sign of the Son of Man will appear in heaven, and then all the tribes of the earth will mourn, and they will see the Son of Man coming on the clouds of heaven with power and great glory. 31 And He will send His angels with a great sound of a trumpet, and they will gather together His elect from the four winds, from one end of heaven to the other.
The elect will be gathered from the doomed city before the destruction. Jesus would come & supervise the deliverance of the elect before the destruction, & would ensure the fulfilment of his prophecy before
this generation passed.
The other comings in the chapter relate to the passing of heaven & earth - the final coming in resurrection & judgment.
So about 35 years later the scoffers challenged his prophecy -
2 Peter 3:3 knowing this first: that scoffers will come in the last days, walking according to their own lusts, 4 and saying, “Where is the promise of His coming? For since the fathers fell asleep, all things continue as they were from the beginning of creation
If they were thinking in terms of the final coming, the question would be irrelevant. No. They were obviously thinking, "Jesus hasn't come as he declared he would.
This generation is fast dying out." Peter assures them that just as God warned of a coming flood, with 100 years warning, & opened the ark for sinners who heeded that warning, though none but the family were saved when the promised flood came, so Jesus' warning of his coming is sure. There's still time to repent - God is longsuffering, but the destruction will come.
Peter extends the warning to all of us, encouraging godly living in anticipation of the final coming in judgment.