However, arriving at those insights is a gradual process: we accumulate the causes and conditions that allow us to see clearly. That is what is meant by the accumulations of wisdom and merit. Without them, we cannot recognize the truth, which is always right in front of us.
We are walking along a dark corridor, advancing many meters in the darkness, relying on the instructions of a helpful guide. Then we come to a turn in the corridor, and as we face that new direction, we suddenly see a bright light. While the vision of the light is indeed sudden, it is only our gradual approach through the dark corridor that makes it possible.