Jude 1:9 Yet Michael the archangel, when contending with the devil he disputed about the body of Moses, durst not bring against him a railing accusation, but said, The Lord rebuke thee.
Jude is using a figure of speech which is not to be understood literally. The event he is referring to is a vision recorded in Zechariah 3.
Zechariah 3:1 And he shewed me Joshua the high priest standing before the angel of the LORD, and Satan standing at his right hand to resist him. 2 And the LORD said unto Satan, The LORD rebuke thee, O Satan; even the LORD that hath chosen Jerusalem rebuke thee: is not this a brand plucked out of the fire?
‘Satan’ is not the fallen angel of Christian mythology. ‘Satan’ is the transliteration of a Hebrew word which means ‘adversary’. The ‘adversary’ represented in Zechariah’s vision was the people in the land who opposed the rebuilding of the Temple and Jerusalem after the return from Babylon.
Ezra 4:4 Then the people of the land weakened the hands of the people of Judah, and troubled them in building, 5 And hired counsellors against them, to frustrate their purpose, all the days of Cyrus king of Persia, even until the reign of Darius king of Persia.
Those who are baptised into Christ become (metaphorically) the ‘body’ of Christ;
Ephesians 5:30 For we are members of his body, of his flesh, and of his bones.
In the same way, the people of Israel who came out of Egypt became (metaphorically) the ‘body’ of Moses by being ‘baptised’ by passing under the cloud and through the Red Sea.
1 Corinthians 10:2 And were all baptized unto Moses in the cloud and in the sea
The remnant of the Jews (the body of Moses) which returned from Babylon was ‘the brand plucked out of the fire’ of captivity.
From Jude we learn that the ‘LORD’ who said "the LORD rebuke thee” in the vision, was Michael the archangel. The Lord’s rebuke, when it came, came through the very specific commandment of Darius and is recorded in Ezra 6.
Ezra 6:6 Now therefore, Tatnai, governor beyond the river, Shetharboznai, and your companions the Apharsachites, which are beyond the river, be ye far from thence: 7 Let the work of this house of God alone; let the governor of the Jews and the elders of the Jews build this house of God in his place. 8 Moreover I make a decree what ye shall do to the elders of these Jews for the building of this house of God: that of the king’s goods, even of the tribute beyond the river, forthwith expenses be given unto these men, that they be not hindered. 9 And that which they have need of, both young bullocks, and rams, and lambs, for the burnt offerings of the God of heaven, wheat, salt, wine, and oil, according to the appointment of the priests which are at Jerusalem, let it be given them day by day without fail: 10 That they may offer sacrifices of sweet savours unto the God of heaven, and pray for the life of the king, and of his sons. 11 Also I have made a decree, that whosoever shall alter this word, let timber be pulled down from his house, and being set up, let him be hanged thereon; and let his house be made a dunghill for this. 12 And the God that hath caused his name to dwell there destroy all kings and people, that shall put to their hand to alter and to destroy this house of God which is at Jerusalem. I Darius have made a decree; let it be done with speed.
The actual body of Moses was buried by the angel of God in Moab and there is no record of a literal dispute over it.
Deuteronomy 34:5 So Moses the servant of the LORD died there in the land of Moab, according to the word of the LORD. 6 And he buried him in a valley in the land of Moab, over against Bethpeor: but no man knoweth of his sepulchre unto this day.
There can be no sensible answer to the question "Why did satan want the body of Moses?” if the dispute is taken to refer to a literal event.
The notion of a fallen angel literally disputing with God over Moses’ dead body is another sound reason for rejecting the idea that the devil and Satan is a fallen angel.
Here is a link to some supplementary reading for you:
I hope you have found this helpful.
God bless you,