Who are the 144,000 spoken of in Revelation 7 & 14 and why?

These 144,000 from the 12-Tribes of Israel are part of the Jewish remnant spoken of by Isaiah (10:22) and Paul (Romans 9:27) and they will ultimately enter Messiah’s Millennial Kingdom immediately subsequent Messiah’s 2nd-Advent manifesting toward the end of the Tribulation era and Messiah’s victory over Russia-China-Islam/Iran who come against Jerusalem via a nuclear war.

The Millennial Kingdom will be focused upon Yeshua receiving the Earthly Kingdom denied Him at His first-advent and the Law Covenant will be partially re-instituted in remembrance of Yahweh’s Covenant with Israel’s children much like Christian’s now partake in Communion in remembrance of what Messiah did for us at Golgotha; difference being, the Law Covenant will be faithfully observed and paradise lost via Adam (Romans 5:12) will be partially restored in the Millennial Kingdom; this, as a stark differentiation between the sin of man/death/horror/disease/suffering and the peace and tranquility that manifests through obedience in the Millennial Kingdom as Satan is interned/imprisoned for 1000-years (Revelation 20:1-10); this, as an example for the faithful angelic creation as they observe the horrors of their former boss, Satan, over the previous 6000-years; the horror of rebellion and rejection of Yahweh’s righteousness compared to the infinite benefits of obedience. This comparison/contrast will act as a bulwark against future rebellion in the Kingdom, the New Jerusalem, where free will remains extant by necessity.