I would go further and say that serendipity is essential in all science. I remember reading something from Claude Bernard, one of the 19th century founders of physiology that went roughly (paraphrased from memory). “I work with an open mind, which is why it happens so often that I discover what I was not looking for, while looking for what I never find”.

This would not fly today. If someone were to find something that was not on their last grant proposal it doesn’t exist, even if they had stumbled on the cure for death, baldness and warts. Science needs room to breath, to make mistakes (which are then corrected by the process of repetition with revision).