I remember as a kid seeing some of Picasso’s earlier work, and in a flash realizing that abstract was a choice. Up until then I had assumed he just wasn’t a very good artist, and was doing the best he could. It changed the whole way I looked at art.
Piet Mondrian is far better known for his geometric abstracts, but likewise, it was a choice. I wish I could ask him why straight lines and primary colors spoke to his soul more than traditional representations.