Because he can see it all.
Nobody is predestined for any judgment except Satan. He is the only one who is guaranteed to be vanquished. You, I, and everyone else it is determined by our actions here on Earth. I could still messed things up and not pass judgment. You could change your mind and become a Christian. Both of these things is possible and God knows this. But which path we take is completely on us. Hopefully that make sense.
OK, then. If he sees
everything, then he knows what we WILL eventually pick, regardless. That does make him responsible when he allows things to happen when he has exclusive knowledge of what we will do; or even when he puts temptations in place that he knows we will succumb to (and will be our downfall).
If he knew Satan would rebel and take one third of the angels with him, that's on him. He put the tree of knowledge in the garden specifically knowing that Adam and Eve would eat the fruit. He allowed Jephthah's daughter to leave his home first
knowing that he would make her a burnt offering to himself (god) (and he didn't stop Jephthah like he stopped Abraham from sacrificing Isaac, which in itself is a messed up test).
Does that not make him responsible when he allows these things to happen when he
has the exclusive knowledge and power to intervene?
Imagine the president knowing a terrorist attack was going to happen in a packed football stadium and just... Letting it happen. Would he not be responsible?