It pretty much comes down to how expected or unexpected the guidance and exceeds/misses are on the metrics of interest.
If you know that FB, GOOG, PINS are all having amazing quarters, you might see SNAPs price rise in advance of their earnings because if some other big ad/social network giants are doing well, surely SNAP will too!
Then there are truly amazing beats or misses by companies and the street tracks those as well.
A more recent example might be Lyft & Uber. Lyft actually came in at the top end of QoQ rev growth and cut losses well. Uber's options market and stock immediately reflected Lyft's earnings report even though Uber was still 24 hours away from reporting. Uber's report was good not great but the stock had already gained in the day prior and thus not much left to squeeze up.
Just my 2 cents on how some of these things happen
I think this is the most accurate way to feel about market movement. People who give you explanations might be right, but how would they even know? Stock narratives are post hoc divination a without much exploration of alternative explanations.
I tell myself that any explanation might be a neat story, but what evidence is there that isn’t just someone’s opinion? (Not much, usually.)
Not trying to be snarky, but this is how I feel about pretty much all AH movement after earnings, for any company. Do you usually not feel this way?