“you will trample on their high places.” In ancient times, “high places” gave the ones who controlled them a distinct advantage in war. They were generally secure and hard to attack. Cities were built on high places whenever they could be, as were Jerusalem and Samaria, the capital cities of Judah and Israel. For Moses to include in his blessing that Israel would trample on the high places of the enemy was a way of expressing that no enemy would be able to withstand them.
When reading the blessings in Deuteronomy 33, the reader is expected to understand that they are conditional on Israel obeying God and worshipping Him. They are not “unconditional blessings” that would occur with or without God’s blessing and help. If Israel wanted to be blessed, they would have to understand that they were being blessed by God, who expected obedience and worship from them, which was part of their covenant agreement. Sadly, Israel did not fully obey God, and as a result did not fully receive many of the blessings promised in Deuteronomy.