The phrase "to a large extent" means that something is done or accomplished to a significant degree. It indicates that there has been a considerable amount of effort put into achieving a particular goal, and it has been successful to a high degree.
Generally, it refers to involvement of large parts of the brain (or the whole organ), instead of identifiable changes confined to parts of the brain. (sciencedaily.com)
At the same time he was a mathematical physicist, and developed his theories in large part in order to comprehend the new findings of physics in the twentieth century. (religion-online.org)
Long - term recovery times are expected, due in large part because of the extent of damage done to the skin. (batonrougepersonalinjurylawfirm.com)