One doesn't necessarily follow the other.
Let me try an analogy.
Say, I know you will eat too much candy. Did I therefore cause you to? Predetermine it? Not necessarily.
Another one.
Say I know a child will make big mistakes, will suffer greatly for them. Yet I chose to have the child anyway.
Did I predetermine or cause its suffering? There are a lot of variations in this area...
Foreknowing is not identical with predestination.
Creating is the same as causing.
Once the creation is settled upon and started, then there is no turning back.
There were other creations that could have been made, but this is the one that was decided upon. Then it was created.
There were other interventions in the creation that could have happened, but this foreknown creation is the one that actually got created.
Imagine that there are an infinite number of creationsa...x that could have been settled upon. This, however, creationx is the one that was the creation actually chosen.
Jesus said of Tyre and Sidon, of Sodom and Gomorrah, that IF His works had been done there, they would have long ago repented. However, His works were not done there. But Jesus acknowledges that they COULD have been. This would have been an alternate creation with a different set of circumstances.
God did not choose that course. He chose this one.
Therefore, all is settled. It was settled at the time of creation.
That is what the appeal to God's omniscience will get us.
But...it's OK. Just trust the Lord with all your heart and lean not to your own understanding.
With that trust, it might as well be true that God simply decided everything ahead of time.
Either way the answer is simple trust in the Almighty.