But that is what you believe to be true, not something God states is true.
Genesis 6:6 And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
Can you explain why it repented God that and grieves over the decision if God already knew man would turn out so badly? I see no room here for God already knowing all this and then still it repents Him and He grieves.
Isa 5:2 And he fenced it, and gathered out the stones thereof, and planted it with the choicest vine, and built a tower in the midst of it, and also made a winepress therein: and he looked that it should bring forth grapes, and it brought forth wild grapes.
"He dug it all around, removed its stones, and planted it with the choicest vine. And He built a tower in the middle of it and also hewed out a wine vat in it; Then He expected it to produce good grapes, but it produced only worthless ones" (Isa. 5:2).
Here God clearly expected one thing but another thing occurred proving in this particular situation showing he did not know what would occur.
A major reason? You're reading English. Translated from the Masoretic text.
The Greek Septuagint (an older manuscript) does not actually use the word we normally translate as repent.
I'm still working on Greek, but here's what I see ...
Gen. 6
6 καὶ ἐνεθυμήθη ὁ Θεὸς ὅτι ἐποίησε τὸν ἄνθρωπον ἐπὶ τῆς γῆς, καὶ διενοήθη. 7 καὶ εἶπεν ὁ Θεός· ἀπαλείψω τὸν ἄνθρωπον, ὃν ἐποίησα ἀπὸ προσώπου τῆς γῆς, ἀπὸ ἀνθρώπου ἕως κτήνους καὶ ἀπό ἑρπετῶν ἕως πετεινῶν τοῦ οὐρανοῦ, ὅτι μετεμελήθην ὅτι ἐποίησα αὐτούς.
6 kai
enethymenthe ho theos hoti epoisen ton anthropon epi tes ges, kai
dienoethe. (Sorry this part isn't pasting properly from source and I can't add the marks)
7 kai epen ho theos apaleipso ton anthropon hon epoisa apo prosopou tes ges apo anthropou heos ktenous kai apo herpeton heos ton peteinon tou ouranou hoti
ethymothen hoti epoisa autous.
I have bolded the relevant words above so that you can check them if you like. Sorry it's rather messy - I'm working from a number of sources and battling my autocorrect as well, lol, and my keyboard lacks the accent marks for transliterated text.
But a more accurate translation would be this:
6 then God laid it to heart that he had made man upon the earth, and he pondered it deeply 7 and God said, I will blot out man whom I have made from the face of the earth, even man with cattle, and reptiles with flying creatures of the sky, for I am grieved that I have made them.
The Greek repent is μετάνοια - metanoia - a word we know well. But that is not what God says he was doing.
Yes, God was obviously displeased with what men had done. But does that actually surprise us? We know that God is displeased when we sin (same thing, He was displeased that men ever sinned at all). But that cannot mean that He had no idea that men would sin, or else how can it be that Christ was the Lamb slain before the foundation of the world?
Just because man did not do as God would have wished us to do, because He did not make us puppets, but gave us free will, does not necessarily mean that man's sin took God by surprise. As I said, I don't think that is even possible, because Christ's sacrifice was planned before man was ever created. God may regret our sin, but He still knew we would before He ever created us. So I don't see how He could be ignorant of the fact.
This took a good deal of effort in searching and typing on a device not optimized for the effort, so I'm not going to do the same thing with Isaiah.
Isaiah 5 is a parable. It illustrates that God gave Israel all that was needed, every benefit, and waited for them to do the right thing, but they did wrong. (The best translation from the Septuagint is waiting for in v. 2.)
The word "expect" can have a different meaning that knowing a certain thing will happen. I don't have time at the moment to see if there's something deeper in the Greek than I know, but we say we expect a thing to be done - we may mean that this is the requirement, the rule, we place on someone. In fact, that's a more common meaning for "expectation" ... rather than to think it means "prediction".
I don't believe I'm contradicting God here. Your point is taken from isolated words in a translated text thousands of years later. Studying the Scriptures is a valuable thing we should do, but it can be very precarious to build a doctrine based on a single (or even a few) words - most especially translations of words. It is a good idea to submit our conclusions to the whole of Scripture. And the whole of Scripture illustrates God repeatedly knowing outcomes, giving prophecies that always come to pass, and speaking of His intimate knowledge of everything. How can a God who knows how many hairs are on the head of every person in every given instant ... not realize that creation was going to fall?
I'm just going on instinct. There may well be much more well-informed knowledge on the subject than I'm offering. But my understanding of God and my reading of Scripture as a whole and my experience in seeing how a word here or there can lead to false conclusions if given too much weight - all point me to doubting your conclusion.
Please understand there is no malice intended, and no desire to argue or condescend. But since you asked me why I said what I did, I'm attempting to explain.