As someone who took DC electronics but not AC, and yet still has to repair shit all the time:
I don't actually know how bypass capacitors work in the circuit design sense, so I imagine they work like prayers. They're saying a little "hail Mary" to ask the gods of electricity to keep the voltages stable.
If you don't say enough prayers, or the cap has shorted and is saying the wrong prayer, your electronic device will not work today.
Add more caps/replace bad caps, and it'll work again.