The previous verse says it all, “for I am God, and there is none else; I am God, and there is none like me,”
“I make known the end from the beginning” is a declaration of His Omnipotence since He is not restricted by time as we are instead He lives in eternity and not time, His Omnipresence since He is all places at all times He is literally in the beginning but also at the end and most importantly His Omniscience; The all-knowing God does not seek knowledge He is knowledge personified and there is absolutely nothing that He does not know including the most remote future events. Others would have to see the end in order to know the end but He is able to see the end even from the beginning.
The prophetic nature of God is an attribute that was lacking among the many other Canaanite deities of that era so to assert His superiority over anything else considered to be God this statement was made. The question is asked in verse 5 “To whom will ye liken me, and make me equal, and compare me,” in other words He stands alone as God; matchless and unparalleled and one evidence of this truth is the fact that He can make known the end from the beginning or prophetically declare the culmination of all things.