Past Expectations and Beliefs with Thought
When talking abut what we think is going to happen in the future, we can use think + will / going to.
I think they’re going to be very happy together.
She thinks you’ll get sick if you eat any more cake.
Now imagine it is several weeks or months later, and we’re describing the same thoughts, but they’re now in the past. We often use this form to compare what we thought in the past with what actually happened:
I thought they were going to be very happy together. (In fact, they aren’t happy together.)
She thought you’d (you would) get sick if you are ate any more cake. (And that’s what happened: you ate more cake, and you got sick.)