He was probably wondering why things happen in the first place. If I remember correctly, he was planning to understand electromagentism better.
There is an incredible biography by Abraham Pais, “Subtle Is The Lord“: https://www.amazon.com/Subtle-Lord-Science-Albert-Einstein/dp/0192806726
Have a look at Pais’ biography of Einstein. The book is definitely more of a scientific bio than a biography of his life.
Subtle Is the Lord: The Science and the Life of Albert Einstein https://www.amazon.com/dp/0192806726
While Einstein ‘loved mathematics and science,’ he ‘disliked grammar and had problems with spelling,’ which could suggest that he had dyslexia. It was falsely claimed that he could not speak until the age of four, but according to Abraham Pais in Subtle is the Lord: The Science and Life of Albert Einstein (Oxford University Press, 1982), Einstein spoke in full sentences between the ages of two and three.