It is common for Christians to confuse the various comings of Christ mentioned in the New Testament.
I have frequently preached on different aspects of the different comings of Christ.
His first coming or Advent was predicted in the Old Testament and took place when He was born of the virgin Mary in Bethlehem.
He came to do the will of His Father Who sent Him Jn 6:38, ‘to fulfil the law’ Mat 5:17, ‘to seek and to save the lost’ Lk 19:10, ‘to call sinners to repentance’ Lk 5:32, ‘that they might have more abundant life’ Jn 10:10. As a result, He came ‘to send a sword’ of division on Earth Mat 10:34 because of the different attitudes towards Him and His message of salvation.
He left Earth to go to Heaven with the promise that He would come again at the Last Day to raise the dead Jn 6:39-40,44-45, Jn 11:24 for the final judgment of the world Jn 12:48 and Rev 22:12.
However there are various ways in which Christ comes between this First and Second Advent.
God visits regularly to see if people bear fruit and Jesus visits these same people to encourage fruit-bearing Lk 13:6-8.
Jesus comes for His people at their death. When going to Heaven He said: ‘If I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there you may be also’ Jn 14:3.
Every time a person dies, ‘the dust returns to the earth as it was: and the spirit shall return unto God Who gave it’ Ecc 12:7.
In 2Th 2:1-2 Paul deals specifically with the mistake that the Thessalonians thought that he had said in 1Th 5:2-3 that Christ would come soon whereas he had said He would come suddenly. Many people, even academics, continue to make the same mistake. The academics in David Suchet’s two-part documentary In the Footsteps of St Paul in 2012 made the same mistake repeatedly. I emailed Suchet’s agent about this, but I received no acknowledgement.
Paul asserts that there are a series of events which must happen before the Second Advent of Christ 2Th 2:3 so that Paul did not expect Christ’s Second Advent to be any moment. If Paul did not think so, then neither should we. However Christ may come for us personally by death at any moment, for which we are to be always ready Mat 24:44, Lk 12:40 and Jn 7:6.
He will also come by His Word and Spirit to bind Satan and usher in the biblical millennium Rev 20:1-7 predicted in Old and New Testament Scripture.