This victory was a gift from God. The description in this passage makes that clear.
God’s blessing determined the outcome of the battle. Moses showed this by raising his hands. When his hands were lifted up, Israel prevailed.
This pattern appeared again and again when Israel entered the land of Canaan. When God blessed them, they succeeded.
But without God’s blessing, Israel could do nothing. They failed when they tried to fight on their own (see Numbers 14:42–45; Joshua 7:10–12).