We grow up believing that the world "out there" is solid and independent of us. We assume that a tree in the forest has bark and leaves and a specific location, regardless of whether anyone is looking at it.
We assume that the past is a library of fixed events that have already happened and are now closed books. This experiment shatters that assumption.
It tells us that a photon does not have a history. It does not have a path. It does not have a shape. It is just a cloud of infinite possibilities waiting for a question to be asked. Until we set up the detector and ask "Where are you?" or "How did you get here?", the photon has not decided on an answer.
And because quantum mechanics does not respect our human concept of time, the answer we force it to give today defines what it must have been doing yesterday.