Satan opposes God. The fact that God buried Moses in an unmarked grave confirms He didn't want the body found. Likely the reason was to prevent the grave from becoming a shrine, since the Israelites struggled with idolatry.
So if we base it only on these facts that we know, the motives of satan can be seen.
Some say satan (the accuser) was protesting a future resurrection of Moses.
But I think the lesson to be learnt is actually in how Michael dealt with satan....
Jude 5-9: "But I want to remind you, though you once knew this, that the Lord, having saved the people out of the land of Egypt, afterward destroyed those who did not believe. And the angels who did not keep their proper domain, but left their own abode, He has reserved in everlasting chains under darkness for the judgment of the great day; as Sodom and Gomorrah, and the cities around them in a similar manner to these, having given themselves over to sexual immorality and gone after strange flesh, are set forth as an example, suffering the vengeance of eternal fire. Likewise also these dreamers defile the flesh, reject authority, and speak evil of dignitaries. Yet Michael the archangel, in contending with the devil, when he disputed about the body of Moses, dared not bring against him a reviling accusation, but said, “The Lord rebuke you!”